@patrik See our other replies in this thread. Start by building the latest version available in fdroid and then try to update to the latest upstream release. Feel free to drop by our IRC/matrix channel for questions.
@patrik or to better answer your question I guess: follow upstream releases/developments and make sure fdroid stays up yo date and can build the latest release.
One of the first Mastodon instances, there is no specific topic we're into, just enjoy your time!