I implemented this mode in a Django library [0] (demo on www.pastery.net) because I love the idea of not needing a password manager any more, just simply having a key with you to log in anywhere, but it doesn't seem to have widespread browser support yet.
Maybe I made a mistake, but Firefox doesn't seem to work very reliably with it, and mobile support is spotty too.
Yes, resident credential (aka "Client discoverable") support in (at least) desktop Firefox is broken and has been for a long time. I believe it's also absent (but at least not broken) in desktop Chrome. :/
Maybe I made a mistake, but Firefox doesn't seem to work very reliably with it, and mobile support is spotty too.
[0] https://pypi.org/project/django-webauthin/