My passkey is synched with iCloud which has all hardened settings set to on, so if I switch devices (I have) its seamlessly. You can also export Passkeys is my understanding but I have not tried it.
When I'm on non-Apple I can scan a QR code on my phone and it will validate it the same way, using bluetooth to send enough info to the target computer to get me logged on.
When I'm on non-Apple I can scan a QR code on my phone and it will validate it the same way, using bluetooth to send enough info to the target computer to get me logged on.