X11 only. Not Wayland.
The engine puts its window at desktop level and makes it input-transparent using X11 extensions. Wayland deliberately does not allow either, so there is nothing to fall back to — it will not run.
Ubuntu 22.04 and later log you into Wayland by default. At the login screen, click the gear and choose “Ubuntu on Xorg”. On Zorin OS, Mint Cinnamon and Xfce you are already on X11.
Check which you are on
echo $XDG_SESSION_TYPE