I can still confirm bug. Fully updated Ubuntu 20.10 - thunderbird 1:91.3.1+build1-0ubuntu0.21.10.2 - mutter 40.5-1ubuntu3~21.10.1
But after commenting "export MOZ_ENABLE_WAYLAND=1" like suggested in comment #18 problem stops. All is working fine now.
I can still confirm bug. Fully updated Ubuntu 20.10 1+build1- 0ubuntu0. 21.10.2 21.10.1
- thunderbird 1:91.3.
- mutter 40.5-1ubuntu3~
But after commenting "export MOZ_ENABLE_ WAYLAND= 1" like suggested in comment #18 problem stops. All is working fine now.