Do you have any information when any major websites will (may?) support U2F in Firefox? Google, FB etc. Is there some issue with Firefox U2F implementation maybe? Thanks.
From what I understand, Firefox doesn't implement the whole U2F spec, and Google and Facebook use some of the features (appID facets) FF left out. However, Firefox, Chrome and Edge all plan to implement the whole Web Authentication API.
Github works fine with U2F in Firefox, I think the problem is just that Google is doing browser detection rather than capability detection. (Of course they do, since they want to underhandedly promote their own browser).