I see a lot of people using https://luma.com/. I'm sure it's not as big as Meetup but it does have a decent community of users, and you can set up pretty much anything with their free plan.
Luma doesn't do discoverability well unfortunately. Also very tech centric.
At least in the Bay, Luma and Partiful are much bigger than Meetup now.
I had a good giggle when I opened their homepage and it looks exactly like the Performative-UI library[1] currently in the #1 spot.