authy and phone also defeat one purpose of u2f, in that they are trivially phishable Any backup for a u2f that isn't another physical u2f is compromising in so

authy and phone also defeat one purpose of u2f, in that they are trivially phishable Any backup for a u2f that isn't another physical u2f is compromising in some way, it's just a matter of which way. In reality though I agree with you and use one time code backup for u2f, and just trust that I will be careful if I ever need to use them. (But maybe I'll be panicking already and get phished? Who knows...)