On Sunday November 19 2023 22:39:29 Dave Close wrote:
>It seems to me that this is unlikely to be a KDE problem, especially
>since KDE starts great under X11. I'm just hoping someone will be
>able to help me understand why this is failing. There are some online
>references to a problem with the /dev/dri/card0 device but they are
>ancient and don't seem relevant.
DRM: https://en.wikipedia.org/wiki/Direct_Rendering_Infrastructure
DRI: https://en.wikipedia.org/wiki/Direct_Rendering_Manager
This sounds like the driver for your GPU is either missing, buggy, or misconfigured. Starting X11 manually will then probably launch a "compatibility" mode where the goodies like compositing are disabled (SDDM may disable that possibility, I don't know). Wayland needs those AFAIK, so it's a bit strange that SDDM does start.
Note that there are 2 drivers: the one in the kernel and one in /usr/lib/{,x86_64-linux-gnu/}dri that's probably needed only for video playback (and hw-accelerated encoding).
Is your GPU one that's embedded on an Intel CPU and that requires the i915 kernel module? That one is known to be buggy enough that it's a good idea to keep a known-to-work kernel version installed. The notebook I'm typing this on is running the latest 4.14 LTS kernel at the moment, because every newer version I've tried to date caused the GPU to hang if I didn't disable a number of features (via i915.foo= kernel options) that would degrade performance and/or display quality more than I want.
R.
