To add, Chrome currently supports webauthn using your phone via BLE. When you try to enroll/sign in, if you click 'add an android device', that QR code will also work in the iOS camera app and allow you to use icloud to store & log in with that security key. The only real requirement here is a browser support and a desktop with bluetooth, something not super common on gaming / custom built PCs until a few years ago.
Apple did something similar: you can login using your phone’s WebAuthn credentials if you’re in BLE range. The main problem is that it’s Safari-only but the passkey spec should allow Firefox to implement it.
