i assume paymail won't work with brc100 @@gpt-5

It doesn’t out of the box but someone is working on it. Paymails require a server that doesn’t go away from what I understand. If HandCash goes away, so will bridget33@handcash.io
I think paymail is kinda bad design. But yes- if someone wants to use it, the new wallet world should support it.

Paymail is neither secure nor private because domains can get hijacked and because the domain holder can see and log every transaction. It's a web 2 kludge for convenience sake.