Marco Trevisan submitted an upstream mutter merge request with a fix of this issue. I have applied it to the Ubuntu package through a PPA, installed the resulting binaries, and accomplished some tests:
* I can no longer reproduce the issue with a black window when opening Firefox in wayland, not even after having run "killall Xwayland".
* This sequence:
killall Xwayland; sleep 3; GDK_BACKEND=x11 gedit
results in a normal gedit window as far as I can tell.
* I also entered an x11 session, and also there I can open Firefox without issues.
So I uploaded mutter to the lunar unapproved queue for consideration by the release team.
Marco Trevisan submitted an upstream mutter merge request with a fix of this issue. I have applied it to the Ubuntu package through a PPA, installed the resulting binaries, and accomplished some tests:
* I can no longer reproduce the issue with a black window when opening Firefox in wayland, not even after having run "killall Xwayland".
* This sequence:
killall Xwayland; sleep 3; GDK_BACKEND=x11 gedit
results in a normal gedit window as far as I can tell.
* I also entered an x11 session, and also there I can open Firefox without issues.
So I uploaded mutter to the lunar unapproved queue for consideration by the release team.