nostr:npub1j9jmf9xw7fpj926hkjlm0xa2ye2t7rp32yw2elxlhat3dtfuhyas3dnl78 I think it is the Signal app though with the DID requirement? I'm not sure the protocol actually needs it.

The real reason tho for the interoperability, is not really for us non-WhatsApp users to connect, but I think more for existing WhatsApp users who want to leave, but feel trapped by having most of their friends only using WhatsApp.