This new passkey stuff adds use of your phone as an authenticator with a laptop or other system via bluetooth with (unfortunate) cloud-mediation. Before that,

This new passkey stuff adds use of your phone as an authenticator with a laptop or other system via bluetooth with (unfortunate) cloud-mediation. Before that, some phones could already offer their embedded security chip as a U2F authenticator with the browser app. E.g. I setup the Titan chip in my Pixel 5a as another authenticator with a Google account. But, it only works with a browser on the phone itself. Since the phone browser can also access a Yubikey, I could use the Titan chip to enroll a new Yubikey or vice versa. I do wish there was a standalone "security key" USB mode I could select alongside file transfer, picture transfer, tethering, or charge-only. Then, I could more reasonably use the phone's embedded security chip as a redundant U2F key for many different services I would normally only access from a PC.