I’m using thunderbird-beta-bin version 71.0b4 on Arch Linux with Wayland on GNOME 3.34.2 and the application opens fine, but crashes when trying to reply to a message.
I am running Thunderbird with env MOZ_ENABLE_WAYLAND=1 to enable better HighDPI and fractional scaling support. I have been running these betas for months and they only started crashing in 71.0b3 and 71.0b4. If I run without the Wayland environment variable the application works as expected (but text is fuzzy, etc).