Most services should have a fallback. Often it is just emailing you a code, or texting a code to a phone number. This is because true, strict MFA would become a

Most services should have a fallback. Often it is just emailing you a code, or texting a code to a phone number. This is because true, strict MFA would become a customer support nightmare - half your users would be locked out from day one. Also realize you can use more than one 2fa device. At the step where it asks you to scan a QR code, you can scan it on multiple devices. Also, you don't need to use a phone to store your codes. 1password can do this for you, and then your codes are available anywhere you are logged into 1pw. The google authenticator app allows you to transfer your codes to another phone, but you need to remember to do that before wiping your old phone.