More to the point, if, like Robert Putnam, you believe that the nation is on the verge of a civic crisis because of the breakdown of local organizations

https://www.joinordiefilm.com/

the goal is to get people to join clubs, so you want some kind of service which has a specific mission and the minimal part is important. You want to put blinders on your users. You don't want them to get served irrelevant ads and notifications. I'd consider this site

https://fingerlakesrunners.org/

which is basically a calendar of events that they host; they have forums but people aren't chewing the fat, they're having discussions that are focused around the events that

https://forum.fingerlakesrunners.org/

You don't have the horrific moderation problems that come out of "is it fake or not?" or "is this socially acceptable or not?" because the real question is "is this relevant to the events we put on?" in which case the problem of "your free speech is (in my view) your obnoxious behavior" which gets worse the more purposeless a site is.