Nip 101 likely allows private(do not expose metadata) e2e #nostr dm by usning alias key which derived from nsec and npub(more details are in the link).

Not understanding fully #Nostr protocol yet, I am not sure it is really private. But If true, It can be better than Simplex because it can be integrated with any clients.

Is there anyone tried this before?

nostr:note10a78r7mvdpautye9ztt85mgcra3ch9us0du38rvvu3uq78fgn3pshd8tj6