Use a 2fa app with backups, or one that syncs to different devices (e.g. authy). It's distributed TFA. The phone number is not very secure, so I don't think it should be a part of TFA. I therefore agree that it is unwise to allow Google to use it for this. I also have a fake dob on my phone account to make Sim porting harder, but you can't trust that you have control over your phone number.