We regret to inform you that Mastodon has decided to leave the F-Droid Reproducible Builds project.
Going forward, Mastodon updates on F-Droid will be maintained by the F-Droid team and signed with an unique per-app key generated by F-Droid.
If you installed Mastodon through F-Droid, please uninstall and reinstall it to keep receiving updates.