KDE Plasma Alt- & Super- shortcuts malfunction when some XKB options are applied on left and right Alt key

As a GNOME user for teen years, I was always interested in KDE. After upgrading to Ubuntu 20.04/Focal from Bionic on my ThinkPad T450, I installed `kubuntu-desktop` to set out migration to KDE.

I'v used XKB to define a customized layout, which containing 4 levels, and utilize the right `alt` to choose 3rd level. The XKB option `ctrl:swap_lalt_lctl_lwin` is also required to re-map the keyboard `ctrl win alt` on left side of `space` to `SUPER_L ALT_L CTRL_L`. ThinkPad has a `prtsc` key on the right side of `space`, between `alt` and `ctrl`. I'v also created an XKB config to remap `prtsc` to `ALT_R`. So the original right `alt` acts as `altgr` to choose the 3rd level, the `prtsc` key can play the role of another `ALT_R` besides.

The bottom row looks like that:
Physical Keys: `lctrl` `lwin` `lalt` `space` `ralt` `prtsc` `rctrl`
XKB Configured: `SUPER_L` `ALT_L` `CTRL_L` `SPACE` `ISO_LEVEL_3` `ALT_R` `CTRL_R`

These settings work perfectly in GNOME for years.
But in Plasma, some strange shortcuts problem happened. `Alt-` and `Super-` related shortcuts stop working! Eg, `ALT-TAB` can't "Walk through windows", `SUPER-D` can't "Show Desktop", etc.

At the very start, I guessed that maybe there are some incompatible statements in my XKB files. So I digged into the XKB configuration files and documentations, compare the system-shipped with manual-written config. Ultimately, I dropped all custom config, just config options provide by XKB. The Plasmas shortcuts malfunctioned! So it's not my custom config fault.

Maybe it's an defect drawn into by Kubuntu? I repeated experiements on MacBook Pro with sole KDE Plasma. Same malfuncation! So it's not Kubuntu fault.

Maybe it's a bug specific to certain Plasms/KDE/QT version? Thanks to ArchLinux on MacBook Pro, the Plasma/KDE/QT is very fresh. Again, same malfuncation! So it's not been fixed in recent.

After many experiments on such difference hardware and OS, I found that the malfunction only happened when all following condictions were met:
- Keyboard layout implicitly includes `level3(ralt_switch)` to enable right `alt` key as `ISO_LEVEL_3`, or "Key to choose the 3rd level: Right Alt" is manually checked in keyboard options.
- Choose additional XKB option to remap left `alt` key

If I disable the right `alt` key to level3 switcher, and everything works properly again.

So if I remapped the left `alt` key, the right `alt` key couldn't be level3 switcher. If I use right `alt` key choose the 3rd level, the left `alt` key couldn't be remapped! How damn ridiculous!

But, don't forget, such above setting works perfectly in GNOME for years. There is something wrong in KDE/Plasma to co-operate with XKB.

I know that many european keyboards have `altgr` key to switch the 3rd level. The layout used by European users probably includes the `level3(ralt_switch)` implicitly. And a linux geek probably like to remap his keyboard to suit one's own taste. But has no body found this bug yet?

Any guy here can confirm this same problem? Perhaps I should report a bug.

------------------------------

System Info:
Thinkpad T450 (ANSI Keyboard)
- KDE Plasma Version: 5.18.5
- KDE Frameworks Version: 5.68.0
- QT Version: 5.12.8
- Kernel Version: 5.4.0-31-generic
- OS Type: 64-bit
- OS: Ubuntu 20.04

MacBook Pro (ANSI Keyboard)
- KDE Plasma Version: 5.18.5
- KDE Frameworks Version: 5.70.0
- QT Version: 5.14.2
- Kernel Version: 5.6.13-arch1-1
- OS Type: 64-bit
- OS: Arch Linux

------------------------------

Below are the steps to reproduce.

NOTE:
- For the sake of unambiguity, `SUPER` is always used as the modifier name of `Win` or `Command` keys, instead of `META` used in KDE shortcuts settings (in which the label `META` represents `Win` key on PC, `Command` key on Mac, `Meta` key on Unix).
- The phisical key is represented in `lowercase`, eg: Win key `win`, Alt key `atl`, Left Alt key `lalt`, Right Alt key `ralt`, etc.
- The modifier symbol is represented in `UPPERCASE`, eg: `SUPER`, `ALT`, `ALT_L`, `ALT_R`, etc.
- Expected intepreted key combination is represented in parentheses along with phicial keys pressed, eg: `alt-tab` (`ALT-TAB`), `win-d` (`SUPER-D`), etc.

In Plasma, Reset such global shortcuts default for test, eg:
- `ALT-TAB` Walk through windows
- `SUPER-D` Show Desktop
- `SUPER-Q` Activities…
- `SUPER-TAB` Walk through Activities

First, open System Settings > Hardware > Input Devices > Keyboard.

For simplicity, Choose keyboard model 'Generic 104-key PC' in 'Hardware' tab. Choose keyboard layout 'English (US)' in 'Layouts' tab.

Then test combinations of different variants in 'Layouts' tab, different options in 'Advanced' tab.

## Keyboard Variant: Default

### Remap left Ctrl/Win keys, keep left Alt untouched
Check all following options in Keybard 'Advance' tab:
- Ctrl Position: Swap Left Win with Left Ctrl

Expect:
- `lwin` key behaves like `CTRL`
- `lctrl` key behaves like `SUPER`
- Of cause, the untouched `lalt`/`ralt`/`prtsc` keys work properly

Effect:
- `lwin` key behaves like `CTRL`:
+ `lwin-c/v/x/z` behave like `CTRL-C/V/X/Z` in editor
+ `lwin-a/e/f/b` behave like `CTRL-A/E/F/B` in terminal
- `lctrl` key behaves like `SUPER`:
+ `lctrl-d` (`SUPER-D`) triggers "Show Desktop"
+ `lctrl-q` (`SUPER-Q`) triggers "Activities…"
+ `lctrl-tab` (`SUPER-TAB`) triggers "Walk through activities" after re-login Plasma, though doesn't immediately.
- The untouched `lalt`/`ralt`/`prtsc` keys work properly

Everything just works.

### Remap left Ctrl/Alt keys, keep left Win untouched
Check all following options in Keybard 'Advance' tab:
- Ctrl Position: Swap Left Alt with Left Ctrl

Expect:

- `lalt` key behaves like `CTRL`
- `lctrl` key behaves like `ALT`
- Of cause, the untouched `lwin`/`ralt`/`prtsc` keys work properly

Effect:
- `lalt` key behaves like `CTRL`:
+ `lalt-c/v/x/z` behave like `CTRL-C/V/X/Z` in editor
+ `lalt-a/e/f/b` behave like `CTRL-A/E/F/B` in terminal
- `lctrl` key behaves like `ALT`:
+ `lctrl-tab` (`ALT-TAB`) triggers "Walk through windows"
- The untouched `lwin`/`ralt`/`prtsc` keys work properly

Everything works as expected.

### Remap left Ctrl/Alt keys and PrtSc key, keep left Win untouched
Check all following options in Keybard 'Advance' tab:
- Ctrl Position: Swap Left Alt with Left Ctrl
- Alt/Win key behavior: Win is mapped to PrtSc and the usual Win

Expect:
- `lalt` key behaves like `CTRL`
- `lctrl` key behaves like `ALT`
- `prtsc` key behaves like `SUPER`
- Of cause, the untouched `lwin`/`ralt` keys work properly

Effect:
- `lalt` key behaves like `CTRL`:
+ `lalt-c/v/x/z` behave like `CTRL-C/V/X/Z` in editor
+ `lalt-a/e/f/b` behave like `CTRL-A/E/F/B` in terminal
- `lctrl` key behaves like `ALT`:
+ `lctrl-tab` (`ALT-TAB`) triggers "Walk through windows"
- `prtsc` key behaves like `SUPER`:
+ `prtsc-d` (`SUPER-D`) triggers "Show Desktop"
+ `prtsc-q` (`SUPER-Q`) triggers "Activities…"
+ `prtsc-tab` (`SUPER-TAB`) triggers "Walk through activities" after re-login Plasma, though doesn't immediately.
- The untouched `lwin`/`ralt` keys work properly

Everything just works.

### Remap left Ctrl/Win/Alt keys
Check all following options in Keybard 'Advance' tab:
- Ctrl Position: Left Alt as Ctrl, Left Ctrl as Win, Left Win as Left Alt

Expect:
- `lalt` key behaves like `CTRL`
- `lwin` key behaves like `ALT`
- `lctrl` key behaves like `SUPER`
- Of cause, the untouched `ralt`/`prtsc` keys work properly

Effect:
- `lalt` key behaves like `CTRL`:
+ `lalt-c/v/x/z` behave like `CTRL-C/V/X/Z` in editor
+ `lalt-a/e/f/b` behave like `CTRL-A/E/F/B` in terminal
- `lwin` key behaves like `ALT`:
+ `lwin-tab` (`ALT-TAB`) triggers "Walk through windows"
- `lctrl` key behaves like `SUPER`:
+ `lctrl-d` (`SUPER-D`) triggers "Show Desktop"
+ `lctrl-q` (`SUPER-Q`) triggers "activities…"
+ `lctrl-tab` (`SUPER-TAB`) triggers "Walk through activities" after re-login Plasma, though doesn't immediately.
- The untouched `ralt`/`prtsc` keys work properly

Everything just works.

### Remap left Ctrl/Win/Alt keys and PrtSc key
Check all following options in Keybard 'Advance' tab:
- Ctrl Position: Left Alt as Ctrl, Left Ctrl as Win, Left Win as Left Alt
- Alt/Win key behavior: Win is mapped to PrtSc and the usual Win

Expect:
- `lalt` key behaves like `CTRL`
- `lwin` key behaves like `ALT`
- `lctrl` key behaves like `SUPER`
- `prtsc` key behaves like `SUPER`
- Of cause, the untouched `ralt` key works properly

Effect:
- `lalt` key behaves like `CTRL`:
+ `lalt-c/v/x/z` behave like `CTRL-C/V/X/Z` in editor
+ `lalt-a/e/f/b` behave like `CTRL-A/E/F/B` in terminal
- `lwin` key behaves like `ALT`:
+ `lwin-tab` (`ALT-TAB`) triggers "Walk through windows"
- `lctrl` key behaves like `SUPER`:
+ `lctrl-d` (`SUPER-D`) triggers "Show Desktop"
+ `lctrl-q` (`SUPER-Q`) triggers "activities…"
+ `lctrl-tab` (`SUPER-TAB`) triggers "Walk through activities" after re-login Plasma, though doesn't immediately.
- `prtsc` key behaves like `SUPER`:
+ `prtsc-d` (`SUPER-D`) triggers "Show Desktop"
+ `prtsc-q` (`SUPER-Q`) triggers "activities…"
+ `prtsc-tab` (`SUPER-TAB`) triggers "Walk through activities" after re-login Plasma, though doesn't immediately.
- The untouched `ralt` key works properly

Everything just works.

------------------------------

Up to now, everything seems good. Then try some complex layouts, eg: any layout containing 3 or 4 levels. These layouts usually implicitly include `level3(ralt_switch)` in its XKB symbol config file.

The variant "intl-unicode" of "us" layout is a good choice for test.

## Keyboard Variant: US, international AltGr Unicode combining

### No remap
Clear all options in Keybard "Advanced" tab.

Expect:
- `ralt` act as level3 switcher
- Of cause, the untouched `lctrl`/`lwin`/`lalt`/`prtsc` keys work properly

Effect:
- `raltb` chooses the 3rd level:
+ `ralt-a/e/o` print `á/é/ó`
- The untouched `lctrl`/`lwin`/`lalt`/`prtsc` keys work properly

Everything works as expected.

### Remap left Ctrl/Win keys, keep left Alt untouched
Check all following options in Keybard 'Advance' tab:
- Ctrl Position: Swap Left Win with Left Ctrl

Expect:
- `ralt` act as level3 switcher
- `lwin` key behaves like `CTRL`
- `lctrl` key behaves like `SUPER`
- Of cause, the untouched `lalt`/`prtsc` keys work properly

Effect:
- `raltb` chooses the 3rd level:
+ `ralt-a/e/o` print `á/é/ó`
- `lwin` key behaves like `CTRL`:
+ `lwin-c/v/x/z` behave like `CTRL-C/V/X/Z` in editor
+ `lwin-a/e/f/b` behave like `CTRL-A/E/F/B` in terminal
- `lctrl` key behaves like `SUPER`:
+ `lctrl-d` (`SUPER-D`) triggers "Show Desktop"
+ `lctrl-q` (`SUPER-Q`) triggers "Activities…"
+ `lctrl-tab` (`SUPER-TAB`) triggers "Walk through activities" after re-login Plasma, though doesn't immediately.
- The untouched `lalt`/`prtsc` keys work properly

Everything just works.

### FAULTY: Remap left Ctrl/Alt keys, keep left Win untouched
Check all following options in Keybard 'Advance' tab:
- Ctrl Position: Swap Left Alt with Left Ctrl

Expect:
- `ralt` act as level3 switcher
- `lalt` key behaves like `CTRL`
- `lctrl` key behaves like `ALT`
- Of cause, the untouched `lwin`/`prtsc` keys work properly

Effect:
- `raltb` chooses the 3rd level:
+ `ralt-a/e/o` print `á/é/ó`

- `lalt` key behaves like `CTRL`:
+ `lalt-c/v/x/z` behave like `CTRL-C/V/X/Z` in editor
+ `lalt-a/e/f/b` behave like `CTRL-A/E/F/B` in terminal

- But `lctrl` key doesn't behave like `ALT` properly:
+ `lctrl` (`ALT`) can active mnemonics underlined, but can't trigger respondent menu
+ `lctrl-f/b` (`ALT-F/B`) doesn't "Forward/Backward one word" in terminal
+ `lctrl-tab` (`ALT-TAB`) doesn't trigger "Walk through windows"

Actually, `lctlr-` key combinations behave like `SUPER-`, rather than expected `ALT-`:
+ `lctrl-d` (`ALT-D`) triggers `SUPER-D` "Show Desktop"
+ `lctrl-q` (`ALT-Q`) triggers `SUPER-Q` "Activities…"
+ `lctrl-tab` (`ALT-TAB`) triggers `SUPER-TAB` "Walk through activities"

- But the untouched `lwin` key doesn't behave properly:
Actually, `lwin` (`SUPER`) itself can only trigger "Application Dashboard". Besides that, it doesn't behave like `SUPER` any more:
+ `lwin-d` (`SUPER-D`) doesn't trigger "Show Desktop"
+ `lwin-q` (`SUPER-Q`) doesn't trigger "Activities…"
+ `lwin-tab` (`SUPER-TAB`) doesn't trigger "Walk through activities"

- The untouched `prtsc` key works properly

### FAULTY: Remap left Ctrl/Alt keys and PrtSc key, keep left Win untouched
Check all following options in Keybard 'Advance' tab:
- Ctrl Position: Swap Left Alt with Left Ctrl
- Alt/Win key behavior: Win is mapped to PrtSc and the usual Win

Expect:
- `lralt` act as level3 switcher
- `lalt` key behaves like `CTRL`
- `lctrl` key behaves like `ALT`
- `prtsc` key behaves like `SUPER`
- Of cause, the untouched `lwin` key works properly

Effect:
- `raltb` chooses the 3rd level:
+ `ralt-a/e/o` print `á/é/ó`

- `lalt` key behaves like `CTRL`:
+ `lalt-c/v/x/z` behave like `CTRL-C/V/X/Z` in editor
+ `lalt-a/e/f/b` behave like `CTRL-A/E/F/B` in terminal

- But `lctrl` key doesn't behave like `ALT` properly:
+ `lctrl` (`ALT`) can active mnemonics underlined, but can't trigger respondent menu
+ `lctrl-f/b` (`ALT-F/B`) doesn't "Forward/Backward one word" in terminal
+ `lctrl-tab` (`ALT-TAB`) doesn't trigger "Walk through windows"

Actually, `lctlr-` key combinations behave like `SUPER-`, rather than expected `ALT-`:
+ `lctrl-d` (`ALT-D`) triggers `SUPER-D` "Show Desktop"
+ `lctrl-q` (`ALT-Q`) triggers `SUPER-Q` "Activities…"
+ `lctrl-tab` (`ALT-TAB`) triggers `SUPER-TAB` "Walk through activities"

- But `prtsc` key doesn't behave like `SUPER` properly:
Actually, `prtsc` (`SUPER`) itself can only trigger "Application Dashboard" after re-login Plasma. Besides that, it doesn't behave like `SUPER` any more:
+ `prtsc-d` (`SUPER-D`) doesn't trigger "Show Desktop"
+ `prtsc-q` (`SUPER-Q`) doesn't trigger "Activities…"
+ `prtsc-tab` (`SUPER-TAB`) doesn't trigger "Walk through activities"

- But the untouched `lwin` key doesn't behave properly:
Actually, `lwin` (`SUPER`) itself can only trigger "Application Dashboard". Besides that, it doesn't behave like `SUPER` any more:
+ `lwin-d` (`SUPER-D`) doesn't trigger "Show Desktop"
+ `lwin-q` (`SUPER-Q`) doesn't trigger "Activities…"
+ `lwin-tab` (`SUPER-TAB`) doesn't trigger "Walk through activities"

### Remap left Ctrl/Alt keys and PrtSc key, keep left Win untouched, disable AltGr
Check all following options in Keybard 'Advance' tab:
- Ctrl Position: Swap Left Alt with Left Ctrl
- Alt/Win key behavior: Win is mapped to PrtSc and the usual Win
- Key to choose the 3rd level: Right Alt never choose 3rd level

Expect:
- `ralt` doesn't act as level3 switcher, but behaves like normal `ALT`
- `lalt` key behaves like `CTRL`
- `lctrl` key behaves like `ALT`
- `prtsc` key behaves like `SUPER`
- Of cause, the untouched `lwin` key works properly

Effect:
- `ralt` key behaves like `ALT`:
+ `ralt-a/e/o` doesn't print `á/é/ó`
+ `ralt-tab` (`ALT-TAB`) triggers "Walk through windows"

- `lalt` key behaves like `CTRL`:
+ `lalt-c/v/x/z` behave like `CTRL-C/V/X/Z` in editor
+ `lalt-a/e/f/b` behave like `CTRL-A/E/F/B` in terminal

- `lctrl` key behaves like `ALT`:
+ `lctrl-tab` (`ALT-TAB`) triggers "Walk through windows"

- `prtsc` key behaves like `SUPER`:
+ `prtsc-d` (`SUPER-D`) triggers "Show Desktop"
+ `prtsc-q` (`SUPER-Q`) triggers "Activities…"
+ `prtsc-tab` (`SUPER-TAB`) triggers "Walk through activities" after re-login Plasma, though doesn't immediately.

- The untouched `lwin` keys work properly

Everything just works.

### FAULTY: Remap left Ctrl/Win/Alt keys
Check all following options in Keybard 'Advance' tab:
- Ctrl Position: Left Alt as Ctrl, Left Ctrl as Win, Left Win as Left Alt

Expect:
- `ralt` act as level3 switcher
- `lalt` key behaves like `CTRL`
- `lwin` key behaves like `ALT`
- `lctrl` key behaves like `SUPER`
- Of cause, the untouched `prtsc` key works properly

Effect:
- `raltb` chooses the 3rd level:
+ `ralt-a/e/o` print `á/é/ó`

- `lalt` key behaves like `CTRL`:
+ `lalt-c/v/x/z` behave like `CTRL-C/V/X/Z` in editor
+ `lalt-a/e/f/b` behave like `CTRL-A/E/F/B` in terminal

- But `lwin` key doesn't behave like `ALT` properly:
+ `lwin` (`ALT`) can active mnemonics underlined, but can't trigger respondent menu
+ `lwin-f/b` (`ALT-F/B`) doesn't trigger "Forward/Backward one word" in terminal
+ `lwin-tab` (`ALT-TAB`) doesn't trigger "Walk through windows"

Actually, `lwin-` key combinations still behave like `SUPER-`, rather than expected `ALT-`:
+ `lwin-d` (`ALT-D`) triggers `SUPER-D` "Show Desktop"
+ `lwin-q` (`ALT-Q`) triggers `SUPER-Q` "Activities…"
+ `lwin-tab` (`ALT-TAB`) triggers `SUPER-TAB` "Walk through activities"

- But `lctrl` key doesn't behave like `SUPER` properly:
Actually, `lctrl` (`SUPER`) itself can only trigger "Application Dashboard" after re-login Plasma. Besides that, it doesn't behave like `SUPER` any more:
- `lctrl-d` (`SUPER-D`) doesn't trigger "Show Desktop"
- `lctrl-q` (`SUPER-Q`) doesn't trigger "Activities…"
- `lctrl-tab` (`SUPER-TAB`) doesn't trigger "Walk through activities"

- The untouched `prtsc` key works properly

### FAULTY: Remap left Ctrl/Win/Alt keys and PrtSc key
Check all following options in Keybard 'Advance' tab:
- Ctrl Position: Left Alt as Ctrl, Left Ctrl as Win, Left Win as Left Alt
- Alt/Win key behavior: Win is mapped to PrtSc and the usual Win

Expect:
- `ralt` act as level3 switcher
- `lalt` key behaves like `CTRL`
- `lwin` key behaves like `ALT`
- `lctrl` key behaves like `SUPER`
- `prtsc` key behaves like `SUPER`

Effect:
- `raltb` chooses the 3rd level:
+ `ralt-a/e/o` print `á/é/ó`

- `lalt` key behaves like `CTRL`:
+ `lalt-c/v/x/z` behave like `CTRL-C/V/X/Z` in editor
+ `lalt-a/e/f/b` behave like `CTRL-A/E/F/B` in terminal

- But `lwin` key doesn't behave like `ALT` properly:
+ `lwin` (`ALT`) can active mnemonics underlined, but can't trigger respondent menu
+ `lwin-f/b` (`ALT-F/B`) doesn't trigger "Forward/Backward one word" in terminal
+ `lwin-tab` (`ALT-TAB`) doesn't trigger "Walk through windows"

Actually, `lwin-` key combinations still behave like `SUPER-`, rather than expected `ALT-`:
+ `lwin-d` (`ALT-D`) triggers `SUPER-D` "Show Desktop"
+ `lwin-q` (`ALT-Q`) triggers `SUPER-Q` "Activities…"
+ `lwin-tab` (`ALT-TAB`) triggers `SUPER-TAB` "Walk through activities"

- But `lctrl` key doesn't behave like `SUPER` properly:
Actually, `lctrl` (`SUPER`) itself can only trigger "Application Dashboard" after re-login Plasma. Besides that, it doesn't behave like `SUPER` any more:
- `lctrl-d` (`SUPER-D`) doesn't trigger "Show Desktop"
- `lctrl-q` (`SUPER-Q`) doesn't trigger "Activities…"
- `lctrl-tab` (`SUPER-TAB`) doesn't trigger "Walk through activities"

- But `prtsc` key doesn't behave like `SUPER` properly:
Actually, `prtsc` (`SUPER`) itself can only trigger "Application Dashboard" after re-login Plasma. Besides that, it doesn't behave like `SUPER` any more:
+ `prtsc-d` (`SUPER-D`) doesn't trigger "Show Desktop"
+ `prtsc-q` (`SUPER-Q`) doesn't trigger "Activities…"
+ `prtsc-tab` (`SUPER-TAB`) doesn't trigger "Walk through activities"

### Remap left Ctrl/Win/Alt keys and PrtSc key, disable AltGr
Check all following options in Keybard 'Advance' tab:
- Ctrl Position: Left Alt as Ctrl, Left Ctrl as Win, Left Win as Left Alt
- Alt/Win key behavior: Win is mapped to PrtSc and the usual Win
- Key to choose the 3rd level: Right Alt never choose 3rd level

Expect:
- `ralt` doesn't act as level3 switcher, but behaves like normal `ALT`
- `lalt` key behaves like `CTRL`
- `lwin` key behaves like `ALT`
- `lctrl` key behaves like `SUPER`
- `prtsc` key behaves like `SUPER`

Effect:
- `ralt` key behaves like `ALT`:
+ `ralt-a/e/o` doesn't print `á/é/ó`
+ `ralt-tab` (`ALT-TAB`) triggers "Walk through windows"

- `lalt` key behaves like `CTRL`:
+ `lalt-c/v/x/z` behave like `CTRL-C/V/X/Z` in editor
+ `lalt-a/e/f/b` behave like `CTRL-A/E/F/B` in terminal

- `lwin` key behaves like `ALT`:
+ `lwin-f/b` (`ALT-F/B`) triggers "Forward/Backward one word" in terminal
+ `lwin-tab` (`ALT-TAB`) triggers "Walk through windows"

- `lctrl` key behaves like `SUPER`:
+ `lctrl-d` (`SUPER-D`) triggers "Show Desktop"
+ `lctrl-q` (`SUPER-Q`) triggers "activities…"
+ `lctrl-tab` (`SUPER-TAB`) triggers "Walk through activities" after re-login Plasma, though doesn't immediately.

- `prtsc` key behaves like `SUPER`:
+ `prtsc-d` (`SUPER-D`) triggers "Show Desktop"
+ `prtsc-q` (`SUPER-Q`) triggers "activities…"
+ `prtsc-tab` (`SUPER-TAB`) triggers "Walk through activities" after re-login Plasma, though doesn't immediately.

Everything works.

I tried again in VirtualBox. This bug can be reproduced on Kubuntu 20.04 LiveCD, but not on KDE neon 5.14.

Probably this bug was brought in by recent Plasma/KF/Qt versions. I've reported this Bug 422038.

Linux/KDE Plasma: Kubuntu 20.04 LiveCD
KDE Plasma Version: 5.18.4
KDE Frameworks Version: 5.68.0
QT Version: 5.12.8

Linux/KDE Plasma: KDE neon 5.14 (20190103-0529)
KDE Plasma Version: 5.14.4
KDE Frameworks Version: 5.53.0
QT Version: 5.11.2

caz,

Thanks for your quite detailed write up of your situation and for filing the bug ticket. It is above my understanding level, but hoping I can contribute nonetheless.

i think I am having the same or a similar issue. I just upgraded from Kubuntu 1804 to 2004 a few hours ago. I could no longer alt+tab nor control+alt+right (my keyboard assignment to move 1 virtual desktop to the right), nor control+alt+left, etc. I couldn't even switch KDE Activities which is using the default meta+tab.

So now, I can finally at least get a window task switcher after disabling "Left Alt is swapped with Left Win", then I am able to successfully "alt+tab" in order to cycle through windows as normal.

I experimented further by logging on as a different user on this same OS instance:
- The different user has "Left Alt is swapped with Left Win" DISABLED/UNCHECKED. Everything worked normal as I could tell.
- Next, ENABLE/CHECK "Left Alt is swapped with Left Win". Was unable to "alt+tab" or do most/all of any other "alt+<...>"-involved keyboard shortcuts.

System Info:
ThinkPad E520 1143AFU
- KDE Plasma Version: 5.18.5
- KDE Frameworks Version: 5.68.0
- Qt Version: 5.12.8
- Kernel Version: 5.4.0-37-generic
- OS Type: 64-bit
- OS: Kubuntu 20.04

keyboard I'm using for all of this: Apple Aluminum Wired Keyboard MB110LL/B (US) (A1243) kernel id 05ac:024f
(sorry, I did not test the physical on-board laptop keyboard)

I can confirm the same behavior on Kubuntu 20.04 as reported by caz, any news on this issue ?

Here are my system info :
Operating System: Kubuntu 20.04
KDE Plasma Version: 5.18.5
KDE Frameworks Version: 5.68.0
Qt Version: 5.12.8
Kernel Version: 5.4.0-54-generic

Did you file a bug?

Hello!

As I am using a custom keyboard ¹layout «everywhere» and I cannot confirm this to be a general problem. I know there are issues with Ubuntu-based dsitributions as they messed up something between 18.04 and 20.04. I came across these problems while trying to dynamically switch layouts in virtual machines (I do only have ubuntus and KDE neon as qemu/kvm-machines).
In Ubuntu Budgie it is possible to have to layouts in parallel with two different language selectors in the tray, playing around with localectl and setxkbmap and relogin.

Can you please check your layouts as interpreted by xkb? First thing to look at are the level keys, using `xmodmap -pm` as you cannot use every key as a level modifier. This depends on how they are physically wired, so perhaps the PrintScr is the first problem to look at. I'm using Scroll and NumLock as Level5-modifiers that work.

Next step is to look at special keys like XF86{whatever} as they could break the layout. Depending on the base language of the layout it could also be necessary to export the correct language in the user-profile. To make a custom layout based on «us altgr-intl» work, you have to `export LANG=en_US.UTF-8`. I don't know why, but I came across this as some dead_{keys} were not working.


¹: custom layout as in «I have a layout in /usr/{local/}share/X11/xkb/symbols/, including advanced variants to handle the keypad.»