For what it is worth, I looked to see if anyone had done Nostr over Gossipsub and I came across a project called Gossip. Looks like they are trying to use the Nostr protocol in a psuedo-gossipsub way. That coupled with the proposed Nostr NIP 72 which would allow Lemmy-like communities could make this the solution you were looking for. Obviously these are in their infancy, but it may be an idea to follow.