I use a passkey with discord on my phone. If I want to log in to discord on a computer it shows a QR code on the page/desktop app and I scan it with my phone to log in. I could see this become a pretty common pattern.
I like it because I can use discord on even a pretty untrusted computer without providing it any credentials or access to my passkey, and then later when I'm done I can revoke the session.
so you need to have discord installed in your phone.
now multiply it with every web site you want to access.
Ok but now do a service that doesn't support that, whether or not it might in the future 'become a pretty common pattern'.