Ask HN: Organize local communities without Facebook?

I want to move our local communities off Facebook and onto our own platform. Is there a off-the-shelf solution or any collaborators I can join to move something along?

EDIT: I live in a more rural community (moved from a big city). We have 5-6 small (~50k people) towns, all well connected. Everything happens on Facebook. I would like to move to a different platforms. Plus points for self-hosted, federated.