Updating #mastodon went great! The instructions underneath https://github.com/tootsuite/mastodon/releases/tag/v3.2.1 paired with https://docs.joinmastodon.org/admin/upgrading/ didn't help much. I ended up redoing portions of the installation process and had to edit the Gemfile.lock. But managed it in the end...
I am not comfortable with any of the technologies used for mastodon. I am happy I managed to get it working again in the first place. π