There's plenty of alternatives if you're looking for event registration. My preferred at the moment is TicketTailor.com, but there's everything from Eventbrite to Luma to Brown Paper Tickets. Now they won't bring you the community, but you can get community from Discord channels to LinkedIn Groups to X and other social media.

Meetup is awful in that they hold your group hostage and you have no way of moving your members, so if you decide no longer to run the Meetup one day, they will let you walk away, but anyone else can just step up and take over the group and do whatever they want. Even worse than Facebook groups.