I vibe coded a relay proxy with nip42 client auth that works well with strfry.. https://github.com/398ja/nostr-auth-proxy

Yes! It's already in the beta series. I'll write this up in a bit more detail soon. Note that the AUTH is a bit limited, and mostly is used to restrict the writing of protected events (NIP-70). Using AUTH for restricting which notes can be read is not currently implemented. We're still trying to figure out the best approach for this.