New bug reporting workflow:
" Please try switching to modesettings xorg driver."
Reply: "Indeed, that is fixed with modesetting. It also seems to solve another problem I had. Thanks for the input :)"
It's unbelievable how many issues get fixed by just kicking out that Intel driver. I see it myself on one of my systems. On Wayland everything is fine, but when starting on X the rendering is just completely broken due to not yet using modesettings there.