If they wish, they can operate both a Nostr relay and a Cashu mint simultaneously.
We believe that relays will accept ecash issued by as many mints as possible.
nostr:note1xuv2l9e40vm2p05lk6prsn45tfmy4v4kgj6lxwewdxuysdr4wcrsrnva37
Discussion
I think the reverse is better, meaning relays want to accept only from whitelisted mints.
Otherwise, I can spin up a new mint , print tokens and DoS attack Keychat since any new mint by definition can't be in the blacklist.