You can't seem to extract the private keys (no matter where they are stored) so that's both good and bad I guess...
A while ago I looked into passkeys with nostr:npub1qe3e5wrvnsgpggtkytxteaqfprz0rgxr8c3l34kk3a9t7e2l3acslezefe , but the authentication seems to be centralized and even a bit technically complex compared to how we do self-sovereign key creation with Nostr and Bitcoin.
Discussion
That’s a dilemma indeed. The private keys are not portable and ‘free’.