Mozilla just put out the call that 2FA is now required.
I'm not able to get this to work for either scanning or manual entry on https://accounts.firefox.com/settings/two_step_authentication.
I know that add-ons are disabled to a certain extent on mozilla.org, so perhaps this is simply not possible, although from the screenshots, it looks like it was at some point?
https://addons.cdn.mozilla.net/user-media/previews/full/208/208795.png