Hello and thank you for maintaining!
In order for the application icon to work in wayland the .desktop filename has to adhere to the reverse domain standard.
For this application that would be org.thunderbird-beta-bin.desktop.
Would you please be so kind to rename that file so the icon will also work in wayland? Thank you.
Reference: https://community.kde.org/Guidelines_and_HOWTOs/Wayland_Porting_Notes#Application_Icon
Pinned Comments
rko commented on 2020-10-18 21:26 (UTC)
In the interest of correct spelling, I decided to integrate CircleCode's suggested change to fix hunspell and make it required.
Chances are this is opinionated, but I think if you can afford to install Thunderbird, you can also install hunspell.
%u
change not implemented, not sure if this is a good idea.