Using U2F doesn't mean you can't have a fallback to email. There will likely be a "I lost me U2F token" reset on websites which allow you to register a new U2F

Using U2F doesn't mean you can't have a fallback to email. There will likely be a "I lost me U2F token" reset on websites which allow you to register a new U2F token/password. Personally I'm not holding my breath though, people hate extra steps and don't even use password managers when companies pay for them. In the corporate space I feel like they compete with 2FA and it's not obvious this will come out on top in most environments.