Given the timing of this question, wanted to clarify the current state, with the recent support of WebAuthn within Universal New.
Poking around on webauthn.me, my current belief is that using Universal New (SSO) will allow us to take advantage of WebAuthn via Touch/Face ID via iOS and the Mac touchbar as of Safari 14+. This would also apply to Chrome 67+ across those same devices as well as Android devices.
Is this accurate? Am I missing something?