[feld]

Chrome has access to USB and its own code to handle U2F devices. This would require your SSH client to have the same capabilities.

This might work well on Linux/BSD machines, but likely not on OSX due to stagnant unix utility updates and Windows because... well, not a real Unix. Would probably require a heavy wrapper around Putty. Not sure if cygwin and friends would ever work either.

[aroch]

OSX supports PAM auth, U2F is just another kind of PAM. That's how I use my Yubikey.

[feld]

I was thinking that server side it was a PAM module, but client side it was not... for some bizarre reason.

So yeah, I suppose if your platform supports PAM this is feasible.