It's a bit unclear to me what protocol version you implemented? Is it FIDO U2F (CTAP1) or the never updated FIDO2 (CTAP2) which allows passwordless login?

Cheers,
Nek

PS: Another U2F (CTAP1) POC can be found at https://github.com/kyprizel/u2femu which I successfully run on USB Armory Mk II.