Im trying to find a good way to move from Nostr to signal (or any other private messenger) without using Nostr dms and without exposing the signal handle publicly.
Discussion
Right. I think keychat might fit your needs. Nostr DMs but they are encrypted using the signal protocol. Easy to switch to from nostr since it using nostr identities. Sign in with amber and start sending DMs to any other nostr identity.
Only downside is the other person must use keychat too. Other DM clients won't see keychat messages.
That downside might be too much. Most people on Nostr use signal. It seems like adding a message with the handle to the lightning transaction directly to their lnurl might be the easiest way. I just don't know how private that is.
I've done that by DMing a unique random email alias then they email me their signal handle.
Keychat message sent if you want to give it a try.