SDDM not starting if usb mouse connected

Bazzite
4

Workaround (not a definitive fix): Random SDDM black screen – forcing X11 greeter

Note: I’m not claiming this is the root cause or the “official” solution.
This is simply a workaround that has been reliable for me.

Symptoms

  • Random black screen instead of SDDM login screen

  • Happens intermittently (often when USB mouse/keyboard is connected at boot)

  • Switching to a TTY and running systemctl restart sddm makes the login screen appear

  • Plasma Wayland works normally once logged in

Environment

  • Bazzite / Universal Blue

  • KDE Plasma

  • SDDM

  • Wayland sessions enabled

What worked for me (workaround)

I forced X11 only for the SDDM login screen, while keeping Wayland for Plasma sessions.

From a TTY or terminal:

sudo nano /etc/sddm.conf.d/20-x11-greeter.conf

Add:

[General]
DisplayServer=x11

Save the file, then restart SDDM:

sudo systemctl restart sddm

(or reboot)

Result (in my case)

  • SDDM login screen became stable

  • No more random black screens

  • USB devices no longer affected login

  • Plasma Wayland sessions continued to work normally

Notes

  • This does not disable Wayland system-wide

  • Only the SDDM greeter runs on X11

  • This seems to avoid a race condition between the SDDM Wayland greeter and USB/input initialization

How to undo

sudo rm /etc/sddm.conf.d/20-x11-greeter.conf
sudo systemctl restart sddm

Again, this may not apply to everyone, but it’s been a solid workaround for me so far.

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Black screen since latest update