No. I'm not sure whether Xwayland or Wayland is used, and that's part of the problem. In about:support, I have MOZ_ENABLE_WAYLAND=1 but also MOZ_USE_XINPUT2=1,

No. I'm not sure whether Xwayland or Wayland is used, and that's part of the problem. In about:support, I have MOZ_ENABLE_WAYLAND=1 but also MOZ_USE_XINPUT2=1, which I haven't noticed until right now. xeyes doesn't respond at all (window freezes) so I can't tell which backend is actually in-use via xeyes. Finally, I'm using the package manager Firefox, and I'm not sure if that's different than the snap/flatpak. In the OpenSCAD case, I've tried installing various qt-related and wayland-related packages and setting QT_QPA_PLATFORM or QT_DEBUG_PLUGINS, but this either ends in a crash or the same slow behavior.