This is where I thought it was going and, the ideas needn’t be incompatible. If you went local (down to say a zip code/postcode) the individual resources required would be minimal. I wonder if people would be able to contribute a smidge of storage/bandwidth like they do with things like SETI. The local instance/mesh would essentially know your location and sign you up to the right one.

I think something like Nostr would work, as each user would be a node (some allowing broadcast and networking), so moving house or even going on holiday wouldn’t be an issue.