existing on Nostr: As far as I know, some aliasing providers support PGP encryption, like SimpleLogin. ...

As far as I know, some aliasing providers support PGP encryption, like SimpleLogin. Now that Proton owns SimpleLogin, it's a bit of a useful negotiation, as we can continue only trusting one party, if you're already using Proton Mail. Of course, it's useful, only as long as your threat model allows you to trust that party in the first place.