Thanks. So that‡ works on my Windows gaming laptop with Chrome, but not (with the same FIDO2 token) with Firefox including on any of my Linux systems (I don't run Chrome on Linux so did not test). Plenty of work to be done there apparently. Good to know.

‡ Referring to "Go usernameless too" which is the mode where a PIN is needed. All the other modes are just plain FIDO and don't need any further verification, and they work just fine on all my systems with any of my tokens.