Which BSD? :)

I ported u2f-hid-rs (the library Firefox uses) to FreeBSD, it's been in the www/firefox port for a while and now accepted into mozilla-central I think.

The Chromium FreeBSD port also has had U2F support for a while.

FreeBSD.

I'll have to try it the next time I update

I may have got this wrong, but IIRC, Duo use a Chrome-specific implementation; it’s on Duo to use the standard. I remember reading that it’s in their roadmap, but it didn’t sound like it was coming soon.

ive used earlier releases if Firefox on Android even with Duo with no problems already.