nostr isn't p2p, it is just clients and relays. Consider checking out Keet rather than wasting your time (and money) with Urbit, its a p2p messaging/conference application that leverages DHT to make connections, no tokens necessary.
Generally ETH L2s make no sense because ethyrium's entire existence comes from the idea that bitcoin can't scale in layers due to its rigid limitations therefore it was determined that other "chains" to support applications and other usecases must be needed. The term "ETH L2" is an admission that ETH is pointless, yet another half-ass attempt at a narrative shift. It would do you well to avoid anything that uses nonsense jargon like that.