an additonal solution to MFA Authentication is introduced in the event that neither the Authenticator App codes or Phone contact don't work
Recently my previous Mobile device broke & fortunately I had a back up I could simply reinstate the new device. Nevertheless, when it came to the Authenticator App, this fell miserably on it's nose. The generated codes were no longer accepted & the Mobile did not receive the Authentication message being sent when I needed to log into the Azure Portal.
Principally I was locked out. As a one man show, I do not have additional colleagues that have global Admin rights.
I see this could be a problem in the future when more small businesses commit themselves to operating from the Azure Cloud (Office 365). Such matters will also be quite time consuming to support from Microsoft so if I may suggest an additional solution is required here... i.e. The one man show back door.