Ask HN: Open-source tool for communities/groups to connect, share info, support

Looking for an opensource tool that could quickly be setup and configured to support individuals/groups/communities to share information and communicate with each other. E.g. a local area/neighborhood where someone who is isolated due to Corona virus and can sign-up and request supplies/assistance. And where interested people can post offers/information and support moderator and administrator roles.

Self hosted so that privacy is maintained (i.e. not Facebook). Preferably on a low-cost or zero-cost service like DO or Heroku.

I envision someone using this tool to organize a neighborhood or apartment complex by distributing sign-up flyers door-to-door. The sign-up URL could even be customized (generated) to pre-fill the address to make signing up very straight forward.

n.b. I've read the T&C for the 'nextdoor' site and their profit model appears to be selling whatever information they have, to whomever will buy it.