We run 2-3 events per quarter, well at least now after all the COVID restrictions. We stopped using meetup.com after their price changes in 2019, a $2 charge for each attendee didn't make sense for a free event. We now have our own mailing list and a simple signup form (Google Forms, now reform.app).

https://news.ycombinator.com/item?id=21257661 lists other alternatives