This MR just got merged: https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/19125
Which completes the tearing protocol: https://gitlab.freedesktop.org/wayland/wayland-protocols/-/merge_requests/65
So once the mesa update lands, XWayland titles should be able to tear under Wayland, at least on AMD GPUs. Nvidia will have to provide support in their drivers in the future.
Now it’ll be interesting which compositors actually implement it and when. Iirc there’re ready KWin patches since one of the main dev working on this protocol uses it.