Hi,
I am running out of things to try using google so i am seeking suggestions to solve my problem. My second monitor does not show up on System Setting > Display&Monitor. The second monitor mirrors the main monitor at boot until the initram loads. The second monitor worked fine with KDE when i was running Kubuntu 20.04. Now i am running Debian 11 with a minimum KDE install (aka i install debian without DE then 'apt install plasma-desktop sddm konsole dolphin').

I run with an integrated GPU (no discrete GPU in the box) :

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Operating System: Debian GNU/Linux 11
KDE Plasma Version: 5.20.5
KDE Frameworks Version: 5.78.0
Qt Version: 5.15.2
Kernel Version: 5.10.0-9-amd64
OS Type: 64-bit
Processors: 12 × 11th Gen Intel® Core™ i5-11500 @ 2.70GHz
Memory: 15.4 GiB of RAM
Graphics Processor: Mesa Intel® Graphics


Notice that i added the force_probe below to get plasma to work after installation:

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GRUB_CMDLINE_LINUX_DEFAULT="quiet i915.force_probe=4c8a"

I also installed the non-free intel firmware to get rkl_dmc_ver2_02 which was missing in 'pure' debian installation.

Now i do not understand much about xorg but here is xrandr output (HDMI-1 is my working main screen, HDMI-2 is the missing screen):

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> xrandr
Screen 0: minimum 320 x 200, current 1920 x 1080, maximum 16384 x 16384
HDMI-1 connected primary 1920x1080+0+0 (normal left inverted right x axis y axis) 597mm x 336mm
   1920x1080     60.00*+
   1600x1200     60.00 
   1680x1050     59.88 
   1400x1050     59.95 
   1280x1024     75.02    60.02 
   1440x900      59.90 
   1280x960      60.00 
   1152x864      75.00 
   1024x768      75.03    70.07    60.00 
   832x624       74.55 
   800x600       72.19    75.00    60.32    56.25 
   640x480       75.00    72.81    66.67    59.94 
   720x400       70.08 
HDMI-2 disconnected (normal left inverted right x axis y axis)
DP-1 disconnected (normal left inverted right x axis y axis)
HDMI-3 disconnected (normal left inverted right x axis y axis)

> xrandr --listmonitors
Monitors: 1
 0: +*HDMI-1 1920/597x1080/336+0+0  HDMI-1


If i do the following i get the second monitor to mirror (a portion of) the main monitor:

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> xrandr --addmode HDMI-2 1280x1024
> xrandr --output HDMI-2 --mode 1280x1024


and then xrandr gives:

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> xrandr --listmonitors
Monitors: 2
 0: +*HDMI-1 1920/597x1080/336+0+0  HDMI-1
 1: +HDMI-2 1280/339x1024/271+0+0  HDMI-2
 
 
> xrandr
Screen 0: minimum 320 x 200, current 1920 x 1080, maximum 16384 x 16384
HDMI-1 connected primary 1920x1080+0+0 (normal left inverted right x axis y axis) 597mm x 336mm
   1920x1080     60.00*+
   1600x1200     60.00 
   1680x1050     59.88 
   1400x1050     59.95 
   1280x1024     75.02    60.02 
   1440x900      59.90 
   1280x960      60.00 
   1152x864      75.00 
   1024x768      75.03    70.07    60.00 
   832x624       74.55 
   800x600       72.19    75.00    60.32    56.25 
   640x480       75.00    72.81    66.67    59.94 
   720x400       70.08 
HDMI-2 disconnected 1280x1024+0+0 (normal left inverted right x axis y axis) 0mm x 0mm
   1280x1024     75.02*
DP-1 disconnected (normal left inverted right x axis y axis)
HDMI-3 disconnected (normal left inverted right x axis y axis)


But the second monitor still does no appear in System>Display and monitors.

Since Kubuntu worked, i wonder if my minimum KDE install may be missing some piece which configures the screens? Or do i miss some package in debian itself? Or my problem has nothing to do with KDE?

Thanks for any ideas on what i can try or read about!

Maybe you can find a fix here:
https://www.reddit.com/r/kde/comments/l ... d_monitor/

rafaellinuxuser wrote:Maybe you can find a fix here:
https://www.reddit.com/r/kde/comments/l ... d_monitor/

Thanks.

Although it is not the same symptoms as i have, i did try to remove the kscreen directory but that did not help.

In the meantime, i also tried another monitor and the 3rd video output (DP) and the problem remains.

You very likely miss some packages. Since I have never used a "minimal" version and never felt the need to (and don't really understand your use case, certainly not a "noob" use case), maybe check your installation again and go through the package list of your distribution to see what you might miss? Plasma-desktop being a meta package in most distributions I don't know what is packaged by Debian in this particular case.

Mind you, there are two different packages, one is called plasma-desktop, the other one kde-plasma-desktop (which include some applications), you might also need plasma-desktop-data and/or plasma-desktop-dev

In Kubuntu there is also kubuntu-settings-desktop that is installed automatically by the plasma-desktop meta package, maybe there is something in it Debian misses?

FWIW: if you are a noob, using the default installation is usually the way to go and learn from there... YM2C

Thanks a lot for the pointers: i will try to understand better the delta.

Fair comments on my config. Before switching away from kubuntu to debian with 'minimal KDE', i asked for advice and i was told: 1) expect some driver problems 2) you will learn a lot more... both comments were right on the mark

My motivation is to minimize what is installed on the metal because i use the host only to run VMs. At the end of the day, it is more important to me than the 2nd monitor if i cannot solve the problem.

I'm sure you choose Debian and Plasma for some specific reason, but my suggestion is to try another distro that allows you to use other desktops. As an openSUSE user myself, I would suggest you try installing openSUSE from the LEAP LIVE version with the LQXT desktop or the derivative versions, among which you will find such lightweight desktops as "Budgie" or "Barebones", which you can try.

I found some new info but no solution... the short version for this forum is that my problem probably has nothing to do with KDE.

The long version:

- The grub command line option i915.force_probe=4a8c (which is required in order to run with 5.10 on my rocket lake GPU with one monitor) apparently also disables the dual monitor supports, at least in some configurations. Now i only found one mention of that unexpected fact but that's consistent with my case.

- Haha, so a newer kernel will surely work with my relatively recent CPU without that troublesome option! So i tried the shinny 5.14 backport without that cyclopic option, but alas it hangs early while booting when more than one monitor is attached and that's also a known issue.

-The good news is that apparently someone tackled the problem in ubuntu so hopefully that will eventually make it in some kernel some day. That also could explain why Kubuntu was supporting the dual monitors in my setup.

Hey, folks. I'm extremely grateful for your help with that issue. I've recently bought a Dell monitor, according to the reviews on productz.com. I've finally managed to connect it due to your helpful advice. Thanks a lot! Tbh, I'm a real fan of flight simulators, so that's the reason I've bought the second screen. I've never enjoyed playing so much. As far as I know, Dell's monitors are the best. So, I still have no regrets about this purchase. So, thanks again, guys. Wish you all the best. Keep the thread updated.