simplex need not advertise server dns or IP at all - completely wrong someonce can attack private server - yes only dns exposed can be attacked

nobody knows who is running nostr relay also - gov harvesting via relay too or @jb55 can forced to be secret service also - that why everyone run own relay. that whole point no need know who running relay or server 

 Do you entrust your children to people you don't know?

See....

Then don't let your private communication go through “relays” whose operators you don't know!