Direct scanout of Xwayland windows doesn't work on Nvidia
I'm using the nvidia beta driver 495.29.05, along with egl-wayland 1.19 and latest xwayland git. This is on KWin 5.23.1 with this MR on top. KWin debug logs show that normal wayland windows successfully scanout, but Xwayland windows fail due to an unsupported output modifier here.
This is after patching kwin to fix scanout in general after it seems to have been broken in general, see this issue.
Edited by sporif