@liaizon can be done now, with existing Mastodon/Fediverse; I've seen the Fedi already being used to find short term and emergency accomodation for people but Fedi could do with either groups or a dedicated app. Might be worth investigating *why* Couchsurfing did this; was it simply for basic running costs or to pay lawyers/PR people following safeguarding failures and criminal cases a few years ago?