0.76 should only exist for the Play Store. Donation links had to be removed in the Google Play variant: https://github.com/LemmyNet/jerboa/commit/ea2776441b4f76ff66f7beb7b64e5291101af5c5.
Not sure why F-DROID would pick up changes from a different branch and build them.
Google wants your app to handle payments through Play Services so they can get a cut. I think it’s technically allowed now to have external payment links in certain cases, but sometimes it’s just easier to remove the thing Google is mad at even if they’re in the wrong.
Again, though, that commit is only for the Google Play variant. Maybe some weird branch merging thing happened and it ended up in the main branch accidentally, but it shouldn’t have made it to F-DROID.