FediHood is a social network built around the place where you live. You choose a city and the topics you care about, then read what neighbours are saying and join in.
It stays a normal fediverse app. Your posts can reach Mastodon, PixelFed, Misskey and the rest, and posts from those servers reach you too.
Source code: https://git.holos.social/tom79/FediHood
There’s only one instance so far: https://fedihood.social/
If new instances are created, they should show up here: https://fedihood.fediverse.observer/list
I don’t know of any, but check out the matrix.org youtube channel: https://www.youtube.com/c/Matrixdotorg they made presentations through multiple matrix conferences about how are they fixing multi client encryption