Please people who put on events I'm begging you, have a mailing list or a physical website where I can look up dates in advance. Just saw a post on Instagram about a craft workshop I would have liked to go to but didn't see before hand, asked the artist if she had a mailing list and was told "no but I post all my upcoming workshops on Instagram and Facebook". I don't think a lot of people realise these don't show most of your posts to your followers, and what they do show isn't chronological?

@afewbugs just found out about https://joinmobilizon.org/en/ fir events and am looking forward to trying it out...

Far as I know, the streams repository has the only existing ActivityPub/ActivityStreams compliant event system.  Hubzilla and Friendica also support events, but were originally built for earlier federated standards and need a few somewhat minor changes to support the current standard. All of these inter-operate today.

Mobilizon doesn't federate events in a manner that works with any fediverse compliant implementations -- at all; and the developers have expressed no interest in cross-compatibility with other fediverse event implementations. So it's an interesting project, but caveat emptor.