This holds true for any 2FA solution, and is generally solved by services that use this kind of technology (e.g., in the form of FIDO U2F) to allow you to regis

This holds true for any 2FA solution, and is generally solved by services that use this kind of technology (e.g., in the form of FIDO U2F) to allow you to register more than one device (so you can have a backup key) and crucially, to allow you to generate a large set of security codes that can be used once to reset access to the service. These codes you would ideally print out and store with your other valuables, or backup in some other manner not dependant on your security keys.