When I open xwayland windows, they usually look like this for a brief moment:

Happens with Plasma, Gnome and Sway. It's less noticeable with Gnome-Mutter. I basically just need to start Firefox OGL (WebRender off) to provoke such artifacts. They disappear entirely as soon as the window content is ready. It doesn't only happen when a process starts, I can also observe it when opening the drop-down menu in Firefox to open addresses from history.

As a sidenote: Very rarely, I can also observe the same kind of artefacts when opening programs inside a native Xorg session (the screenshot shows starting Doom in Wine, but the xwayland artefacts look exactly the same). My impression is that the affected programs always use 3D acceleration (either OGL or Vulkan). It could be that the same is true for the xwayland issue. Maybe they don't have technically the exact same source, but there might be a connection nevertheless?

This is with xorg 1.20.3 and latest amdgpu/mesa drivers (-git & stable). I unfortunately can't test if Intel GPUs show the same behavior.