[wayland]: mutter/gnome-shell fails to start with stalled entries in /tmp/.X11-unix/
gnome-shell/mutter starts Xwayland. Prior to do, it tries to find a suitable display number.
If it fails, it aborts and the session does not start.
It seems however that mutter can get fooled by stalled entries in /tmp/.X11-unix/ and fail to start if such entries are left (for whatever reason) in /tmp/.X11-unix/
Xwayland, like all Xorg servers has the “-displayfd” option which let Xwayland search for an avaialble display (Xwayland deals fine with stalled entries), and then provides the display number to its caller via the fd given on the command line.
mutter should use that mechanism instead of searching for a display itself.