Yet another minor release of Thunderbird is out on November 11, 2020. The app version 78.4.3 comes with two user interface fixes. There is also a long-standing known issue.
Thunderbird is my preferred email client of choice. I use this app on every PC and on every operating system I use. It is stable, contains all the features you need, supports add-ons and also comes with a useful RSS reader. I am using Thunderbird for many years and never felt the need to look for an alternative.
Thunderbird 78 doesn't support classic XUL add-ons any more, but includes some of their features natively. E.g. on Windows you can minimize the app to the system tray.
The following changes have been made in versions 78.4.3
What's in Thunderbird 78.4.3
The release notes are available here.