Don’t see how that would work. Anyone can be a part of any group. Global is pretty much it.
Discussion
You could geofence a server/relay, or do some sort of verification like Nextdoor does to confirm you live in the area.
There are global concerns that affect everybody, so there's a place for global social media. However, when all the platforms are global, important local concerns can get lost in the noise.
Might have to block vpn access too. Not sure it’s really worth it. Build a group by sharing contacts seems like it might work better. Idk 🤷