I think the client needs to be nip-46 compatible. So far it seems to be coracle.social and nostr.kiwi. Haven’t found others.
On coracle.social it shows my npub and the “bunker key” which is the delegated nsec for that client. You might be able to plug that nsec into another client, but unless it was nip-46 compliant I think it would just treat it as a normal nsec and be associated with the delegated npub and not your npub.