@FediFollows had a look the other day afaict it doesn't really exist yet. People say Friendica, Hubzilla, Zap etc, but none of them really do Facebook-like groups (which is what an alternative for is needed imho). The best #selfhosting #opensource thing I found was https://www.humhub.com/ but that's not part of the #fediverse. It looks like @grishka's #smithereen project is headed in the right direction though, see e.g. https://mastodon.social/@grishka/105702974840976514
@jdaviescoates @FediFollows there will be forum-like discussions in Smithereen groups at some point.