Regarding your edit the problem here is that you assume that U2F/FIDO is some sort of a new, separate thing when in fact it can be just one 'program' or applet

Regarding your edit the problem here is that you assume that U2F/FIDO is some sort of a new, separate thing when in fact it can be just one 'program' or applet of your device which can support others, that are more suitable for logins. FIDO just wasn't designed for it. Just because this or some other Yubico devices might not allow it doesn't mean others don't. AFAIK for instance Feitian ePass supports GIDS applet, which you can install on smartcards too. And yes, you can install U2F applet on smartcards also. https://www.rcdevs.com/docs/howtos/epass/epass https://www.rcdevs.com/docs/howtos/epass/epass https://www.ftsafe.com/Products/FIDO/NFC https://www.ftsafe.com/Products/FIDO/NFC Why people are not rooting and fighting for an ability to extend things with open source is beyond me.