First I thought, why would we need a Nostr replacement for Meetup because Meetup does its job well?

But then I realized that with Nostr you can make the meetup app interoperable with other social apps using the Nostr social graph.

And you can build some monetary incentives with zapping, e.g. rewarding the event organizer for a successful event.

Haven’t tried or researched Flockstr at all yet but will try.