Please go to thunderbird.net or to https://www.thunderbird.net/en-US/thunderbird/all/ for all downloads. that is the only way to be sure that you are getting the official release.

At official site there are links to these releases: https://github.com/thunderbird/thunderbird-android/releases which I mentioned at the beginning.

Hmm this is posted in the desktop forum. I, and guess David, have never even heard of this obtainium. Perhaps ask them why they identify Thunderbird that way as I can find no references to it anywhere on the Thunderbird web site. Only the APK link

I will transfer this to the appropriate Android forum and perhaps someone that knows something about the android version and this specialist software you are asking about may be able to help you.

Obtainium allows you to install and update apps directly from their release pages, and receive notifications when new releases are made available. https://obtainium.imranr.dev/

As for mention of pseudo and obtainium. https://wiki.obtainium.imranr.dev/app_tracking/

Thanks for help! After reading documentation you provided everything looks easier.