Thanks for posting. I was scratching to my head as to why ssh with FIDO keys wasn't working with macOS Monterey 12.2 which ships with OpenSSH_8.6p1 (as you say, FIDO support has been present since openssh 8.2). Is Apple rolling their own implementation of OpenSSH? Back to installing OpenSSH with homebrew....

Did disable system integrity protection (SIP) prior to installing the extension/driver?