If you're using a hardware device, you can't extract them, because that's the point.
If you're using a password manager to store your passkeys, there are protocols to move them between password managers.
okay but on apple devices (for instance) I believe the private keys are stored in the icloud keychain, otherwise there would be no passkey portability between your apple devices
okay but on apple devices (for instance) I believe the private keys are stored in the icloud keychain, otherwise there would be no passkey portability between your apple devices