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Need help: xhost + does not work as expected

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Dear developpers,

using KDE neon 5.21.0 in the X11 version, I often work in Konsole. This is my system information:
Operating System: KDE neon 5.21 User Edition
KDE Plasma Version: 5.21.2, also not working in 5.21.3
KDE Frameworks Version: 5.79.0 also not working in 5.80.0
Qt Version: 5.15.2
Kernel Version: 5.4.0-66-generic also not working on
OS Type: 64-bit
Graphics Platform: X11
In the laptop you can find this Processor: 8 × Intel® Core™ i7-3632QM CPU @ 2.20GHz
Memory: 3.7 GiB of RAM
Graphics Processor: Mesa DRI Intel® HD Graphics 4000
Docking station
22" Monitor

Having several users on this one machine, I want to login in a Konsole window as a different user than the account I'm logged in in KDE neon. In former Linux distributions I used
Code: Select all
xhost +
su - "otherUser"

and after having entered the correct password I could do all the work out of this Konsole: starting Kate, starting Firefox, starting Dolphin... always (as needed) as the "otherUser".

When I do the same procedure under KDE neon today, I can log in as in former times. This is working. Also the linux commands in a konsole are working without limitation. But as soon as I want to work with the graphical display using Kate (as example) I get this message:
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"otherUser"@"host" ~/Dokumente/txt $ kate 0_content.txt &
[1] 3631
"otherUser"@"host" ~/Dokumente/txt $ qt.qpa.xcb: could not connect to display
qt.qpa.plugin: Could not load the Qt platform plugin "xcb" in "" even though it was found.
This application failed to start because no Qt platform plugin could be initialized. Reinstalling the application may fix this problem.

Available platform plugins are: eglfs, linuxfb, minimal, minimalegl, offscreen, vnc, wayland-egl, wayland, wayland-xcomposite-egl, wayland-xcomposite-glx, xcb.

[1]+  Abgebrochen             kate 0_content.txt

Happily I can use vi as well. But kate has more comfort... o)

When I work on "xcb" with uninstall and install again - no difference between "apt" or "pkcon" - the result remains the same.
I've already tried to find the answer in this great forum, but I didn't get the clear instruction how to deal with xcb to get kate running in "otherUser" and out of Konsole. I also got no answer, if there is an additional command required, could be similar like "export DISPLAY=<someDisplayInformation>" before entering "xhost +"

The implementation of the bridge from KDE to X11 seems to be some miles away from being ready. "xcb" is not implemented correctly, kwin_x11 is consuming a lot of power - but xhost is not supported... What can I do to get xhost + running? What can I help developer to get information to do the required improvements? Callgrind? Helgrind?

Test to install kwin as mentioned in another post did not help.

After such a long time of patience without any answer, things start to get annoying...

Thanks a lot for your help in advance,

kind regards,



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