@SamantazFox @fdroidorg But you're right that Google doesn't allow this.

The official Mastodon app actually has a special flavour for Google without in-app updater, but the Mastodon team was unwilling to provide .apk files for it (stating that it was too much work to supply that on top of the .aab they build for Google).

And thus, F-Droid was left without an .apk file that was compliant with F-Droid policy. And after a lot of difficulty it was decided to drop reproducible builds, sadly.