https://microco.sm/ https://microco.sm/ was an attempt at this... it's dead as a startup but the code is open source. https://www.lfgss.com/ https://www.lfgss.

https://microco.sm/ https://microco.sm/ was an attempt at this... it's dead as a startup but the code is open source. https://www.lfgss.com/ https://www.lfgss.com/ is one example of about 300 sites that are using the platform. It's recognisably a forum, but works great on small screen devices and includes richer functionality such as events within forums (logically forums are more equivalent to folders that can contain differently structured things, so not just conversations but events as well for example). I'm still tempted to work on it at times (hasn't been updated in many years) but for that to be a motivation I'd want to believe that others would run instances too and it would grow as a self-hosted multi-tenant option. It's extraordinarily cheap to run, far less maintenance than any other forum platform I've ever operated.