This instance set up just for one person, but you don't have to make one for yourself. Visit https://joinmastodon.org/ to find the instance that's right for you.
Mastodonsocial.qutic.com
Mastodon-Instanz der qutic development GmbH. Invites auf Anfrage.
Eldritch Bellowsbellow.el.drit.ch
This server is yet another place in the fediverse. No specific topics, probably nerd stuff.