KWin using GLES uses EGL and it requires some EGL_image extensions, which are not provided by Mesa-LLVMpipe, so compositing fails to initialize. Before 5.23, it would fall back to XRender compositing and work properly. With 5.23, it is unable to start compositing because XRender got removed, and so it disables compositing. Now it however fails to disable compositing properly, and the screen stays black forever, probably because either the overlay window is not properly removed or xcb_composite_unredirect_subwindows is not called. It works when disabling compositing explicitly, so that kwin doesn't even attempt to initialize it.
Git commit 85f8a533604f9f8d8d61aea8987a82a211ea10a0 by Vlad Zahorodnii. Committed on 18/10/2021 at 10:20. Pushed by vladz into branch 'master'. x11: Properly unredirect windows if compositing is not possible Before attempting to create scenes, kwin will redirect windows but if the opengl scene can't be created, it won't unredirect windows, which seems to cause issues on aarch64. M +4 -0 src/composite.cpp https://invent.kde.org/plasma/kwin/commit/85f8a533604f9f8d8d61aea8987a82a211ea10a0
Git commit 140834e75a86153e50c7551802085272cab6bff1 by Vlad Zahorodnii. Committed on 18/10/2021 at 10:31. Pushed by vladz into branch 'Plasma/5.23'. x11: Properly unredirect windows if compositing is not possible Before attempting to create scenes, kwin will redirect windows but if the opengl scene can't be created, it won't unredirect windows, which seems to cause issues on aarch64. (cherry picked from commit 85f8a533604f9f8d8d61aea8987a82a211ea10a0) M +4 -0 src/composite.cpp https://invent.kde.org/plasma/kwin/commit/140834e75a86153e50c7551802085272cab6bff1
I wonder if I've the same problem. When I login (plasma_x11) I see SUSE's light bulb forever. I've to kill KWin, disable compositing and restart KWin. Then I can work again but get many graphical artefacts. This is on Tumbleweed, Plasma 5.23 with Intel UHD Graphics.