What I mean is that if there were some simple way to create a relay in our system, there would be social networks that could be set up inside the nostr social network. It would be true decentralization, it would be something like Freenet pages that are only shared between groups of trusted people

Can you explain this? How is the phone the server? It would be nice if you could use NOSTR for private groups of friends or acquaintances without exposing your posts to strangers, but nowadays it seems very complicated to make a relay in nostr