How do you backup access? The one thing that's stopped me from pulling the trigger on U2F is if that device is lost, stolen, or broken then I'm hosed, right?
With standard 2FA, I have backup devices and codes that I can start restart from scratch if my phone is ever lost/stolen/broken.
Backup codes and (in my case) backup keys. In the corporate world, the backup codes can be generated and shared on-demand, or U2F temporarily disabled if ID can be verified another way.
Write down your backup codes. Register a second key if possible. Google accounts are set up to prompt phones, too. In some cases we still have SMS 2FA enabled.
With standard 2FA, I have backup devices and codes that I can start restart from scratch if my phone is ever lost/stolen/broken.