Got it.

Now Keychat focus on private note, aka chat app. 

I think public note can also use bitcoin ecash stamp. It is also possible his fans pay ecash to get his latest post.

Keychat relay only add collecting bitcoin ecash function. If the relay operator provides free service, current relays e.g., Damus relay can be used as Keychat relay. 

Nostr relay operators can also be one cashu mint. Keycaht now using the third party cashu mints.