For the latter you'll need a browser which supports U2F. Firefox doesn't natively but you can install the U2F addon and then Custom UserAgent String to change your browser's UserAgent to fool Facebook into thinking you're using a Chrome browser which supports U2F.
I've tested it with the Duo Authenticator app and both Yubikey 4 and Yubikey U2F keys and all is good.
More information from Facebook - https://www.facebook.com/help/401566786855239?pnref=...
If I can't drink my bowl of coffee three times daily, then in my torment, I will shrivel up like a piece of roast goat
Spiders on coffee - Badass spiders on drugs
Edited by caffn8me (Fri 27-Jan-17 01:05:38)