On my side I stopped using Meetup as heavily when they removed the free API, and post-lockdown, at least nearer to me, there aren't nearly as many in-person meetups.

In the #IndieWeb community, there's the Meetable project, seen at https://events.indieweb.org/ and is powered by IndieWeb tech (not ActivityPub) if you fancied self hosting, but then you miss out on network effect and discoverability of events you're not necessarily organising yourself 🤔