Monstanner 🐧

Looks right. Then you don’t have to do anything. I mean, it’s up to you, but do you really want to continue using the beta?

It’s easy to find out. Navigate to Thunderbird Beta in F-Droid Basic and look at Versions. If you only have a single version there, then you have to delete it. If it says that no version with a compatible signature was found, so too. If you have three versions to choose from and one of them is installed, then you don’t need to do anything, because then you will get updates.

You don’t have to do anything. K-9 Mail remains K-9 Mail. A mistake was made in the naming process. This will be fixed soon. So in F-Droid the following will be present: K-9 Mail Thunderbird Thunderbird Beta

Thunderbird for Android is based on K-9 Mail, but has received a few changes here and there (e.g. the accent color is blue instead of pink). As mentioned above, K-9 Mail will remain and will probably continue to get the Beta & Stable versions in the version selector. Thunderbird has been split into two apps for this purpose. The settings should usually be able to be adopted from K-9 Mail and vise versa, because of the same codebase (but I haven’t tested it). In the end, it’s up to you whether you prefer the dog or the bird. :)

Edit: Added more info.