Also not a fan of ethereium either, I get it. I’m not a dev, but practically speaking… it is only used to obtain and reboot(if needed) your unique id. Using L2 you dont even need a wallet. Otherwise you don’t have interact with it. Not an expert on the history, but my understanding is when Urbit was built 10ish years ago it was the best blockchain tool available at the time. It was a pragmatic choice. And for whatever flaws of that blockchain choice, at the community level it does seem to practically help prevent spam and bot problems. Thus, P2P support and trust appears much higher than here (in my several weeks of nostr exposure anyway). I’m here to learn about nostr. There are some advantages here, but my main suggestion if one cares about learnings in the P2P space it would leave a gap in knowledge to gloss over Urbit casually.
Discussion
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.