Did that, thunderbird release no beta, and no issues since I don’t have google account. For people with google account requiring to re-sign in, and who don’t often do so, signing in is really hard if they don’t registered their phone number to google. It’s sad, I commented about it in some other post. Understandable in reality they are different apps, but in the end it should be the same user ID, but nevertheless it’s a PITA if people don’t have a device permanently logged in, :( For them it’s better to stay on K9,and hope K9 doesn’t go away, or else find out how the heck to login to google once again.
F-Droid produces its own builds, with its own signatures, so to get f-droid going, you’ll need to install from F-Droid. However the import mechanism seems really nice. Perhaps you can install from F-Droid the official release, which can co-exist with your upstream installed beta release, import from it from the F-Droid app, then remove the upstream installed beta release, and if you wan to keep on beta, then install the beta release from F-DRoid (be careful right now, given a bug made K9 show up as beta release as well, but the app ID is clear, just being careful is enough), and then import from the official release, then remove the official release and you’re all set. The idea is not to reconfigure a thing by doing those steps, and perhaps you wouldn’t like to go to beta, and remain on the official release, which is not that behind, and perhaps better tested.