After upgrading to plasma 5.21.0 I’m unable to use an external monitor on my Laptop (Lenovo C940). When I plug in the monitor using a HDMI cable the display configuration starts to rearrange, but after ~3s and before the external monitor shows an image it flips back. After that it flips back and forth every few seconds until I unplug the monitor. This happens in X as well as in Wayland. While switching back and forth I have seen multiple KDE applications crash with a traceback that suggests an error in the Wayland protocol (plasmashell, kmix, drkonqi, …). (I didn’t try to reproduce this on X). After downgrading to plasma 5.20.5 and without changing anything else in the system it works again. Reproducible: Always Steps to Reproduce: 1. Plug in an external monitor using HDMI while running plasma 5.21.0. Actual Results: The display configuration keeps flipping back and forth between Laptop screen only and the dual-monitor configuration. Various KDE apps are crashing. Expected Results: The display configuration adjusts to the new monitor. No apps crash. Reproduced with gentoo-kernel 5.10.10 and 5.10.17.
Please report it upstream.
...but only after trying with 5.21.1 upgrade available since yesterday, and trying with a fresh testuser profile.
I tested it again with 5.21.1: - It was reproducible with my existing profile. - It was not reproducible with a new user profile. - I could fix it by deleting the contents of ~/.local/share/kscreen Thanks!
