Pheonix does not support zaps. Lightning address or LNURL and supported by Wallet of Satoshi or Alby… You can use your own node and host a lightning address otherwise
Discussion
How do you host a lightning address on your own node?
Different solutions are listet on lightningaddress.com
you don’t host on the node if that’s your question. You need a ln node plus hosting ln address that’s linked to your node… this won’t give you 100% comparability since you would need to implement zaps into your setup but should allow you to receive zaps
So I guess Damus is doing validation and Iris isn’t. Either way the error messages need or be improved. UX is hard.