What about forum software like Discourse or Flarum https://flarum.org? However Discourse is a bit expensive.
In addition, I'm creating a Pay-what-one-wants alternative to FB gropus and Meetup and email lists ... It's sort of a cross between StackOverflow, Slack, HackerNews: https://www.talkyard.io (open source).
What do you like the most about Groups.io? if I may ask
