I have deployed FIDO authenticators at a ~2000 employees organization as the second factor. It was great for a while - when early versions of macOS and iOS respected the “platform” claim and created non-exportable private keys backed by Secure Enclave. Windows was never a problem, keys were created in TPM. We mandated 2 FIDO credentials - typically the laptop and either a phone or Yubikey (or both). People were encouraged to use the later but as soon as the keys were not exportable, phones were acceptable.

Then, Chrome got an update and started hijacking the enrolment process from the operating system and created keys synced to Google Account. This resulted worse UX because authentication now required pulling the Android phone (for those unlucky ones who have it) and confirming the login there instead of doing it right on the computer, uninterrupted.

Then, Apple followed with cloud-only key pairs and then so did the password managers (including Bitwarden Enterprise we were using) and everything become a mess.

The only solution would be to use the key attestation and to only allow specific security keys. Both Chrome and Apple have config knobs to simplify enterprise attestation (a strong assurance, which FIDO authenticator has been used), but neither Windows nor macOS support key attestation for hardware-backed keys (and macOS ignores “platform” claim altogether).

It sucks.