I lean towards "Join Nostr" lately. And then some explainer that on Nostr it's all secured by cryptographic keys - "profile" misses that point even more than "account". I feel it should be "Nostr _network_" (not abc.com) -> "Keys/nsec/npub" -> "Profile, notes, etc". If we don't talk about keys then we might as well just keep using "account".

And I think "what's your npub?" seems like the best option - it's short, it's purpose is same as "handle", it's new and different (people should learn about public keys), and it's shorter than "nostr id/address". OTOH even if we all start using "what's your npub?", I would bet people will be using "npub" to mean nip05 eventually, because nip05 serves the same purpose and is human readable.