I have a fresh install of Debian 11 which I am completely new to. I'm running KDE Plasma desktop and I have an external monitor. Initially everything was fine, but after a reboot, and logging on as normal, both screens are completely blank. The mouse pointer moves across both screens (I set it up to extend the displays across the laptop monitor and the external one), but there is no task bar or menu anywhere. Left and right clicking the mouse does nothing. I can open a terminal with Ctrl-Alt-T, which opens in full screen on the external monitor regardless of which screen the mouse is currently on. With the terminal open, F11 which normally toggles between full screen and normal also does nothing.

Hoping this is just a newbie problem, but I am completely stumped.

  • 1
    Wow !! Your first suggestion worked perfectly ! Do you know why this might have happened, and how to avoid a re-occurrence ? Please write up an answer so that I can accept and upvote :) Commented Nov 9, 2022 at 10:58

1 Answer 1


Not the solution but as a workaround what you could try is pressing ctrl+alt+F2, log in, run loginctl unlock-session and press tab so it autocompletes the session id (like loginctl unlock-session 2), then logout and press ctrl+alt+F1 and see if you can log in and see the screen. Another thing to try is running killall plasmashell and kstart5 plasmashell in the terminal which you can open. If this works, you could debug from there.

If you're using Wayland instead of X11 (X11 is the default) it's caused by bad support for Wayland in the version of KDE used in Debian 11 (hopefully not anymore in Debian 12). If you're not using Wayland, I don't know what caused it.

  • Here I asked about this(?) bug that occurs when using Wayland with an external monitor (includes a workaround).

  • Here I asked about this(?) bug that occurs when using Wayland when waking from standby (this problem regularly happens when waking from standby).

  • I also filed bug reports that are linked there but they were closed because Debian 11 ships version of KDE that are too old.

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