When plasma won't start after a kernel upgrade

Most likely it's something wrong with X, I fixed my issues by adding the following to /etc/sddm.conf.d/10-wayland.conf

[General]
DisplayServer=wayland
GreeterEnvironment=QT_WAYLAND_SHELL_INTEGRATION=layer-shell

[Wayland]
CompositorCommand=kwin_wayland --drm --no-lockscreen --no-global-shortcuts --locale1

Source: https://wiki.archlinux.org/title/SDDM