Passkey on an iPhone, logging into a public-ish terminal by scanning a QR code? Yes.

In fact, if you have your Apple Passwords app set to sync through iCloud, you can:

- Make a passkey on your Mac for a site in the Passwords app

- Go to a different computer (a friend's or whatever)

- Attempt to log in, choose use another device, it'll show the QR code

- Use your iPhone to scan that QR code and sign in, as the iPhone has the passkey synced through iCloud

Note, the same kind of thing is also possible with other password managers as well.