kwinft/disman not resilient toward nonsensical display modes offered by modesetting DDX, causing corrupted output
I use a custom single resolution 85Hz EDID for my display. With it, modesetting DDX offers nonsensical modes: https://gitlab.freedesktop.org/xorg/xserver/-/issues/956
When I set resolution and refresh rate to auto in kwinft/disman settings, display output is a distorted mess. With vanilla kwin/kdisplay, they seem to just ignore such modes when setting them in the UI. While this is probably not a bug in kwinft/disman at all, it might be the lesser evil if the system remains usable. ;)
The issue does not exist with xf86-video-amdgpu DDX or on Wayland. Without custom EDID, the auto mode also works with modesetting DDX and kwinft/disman.
Aforementioned EDID:
Loaded as described here: https://wiki.archlinux.org/index.php/kernel_mode_setting#Forcing_modes_and_EDID