The most universal element in Nostr is the public key as the ID, followed by the relay model, and then the RSS mechanism.
Keychat adopts two elements from Nostr’s design: using public key as ID and the relay model.
nostr:note1ut5t0p9yavx9mrl9jqdt0hmq3n4mvu7thxg3zpehpqaur4g4hucs3ahwss