Outlook has been locked out for days

I am the sole Global Administrator of my Microsoft 365 tenant

My main account has been locked out for days due to a broken Microsoft Authenticator registration (Error 500121).

I have tried:

• Adding GitHub and personal email as alternate methods
• Signing out of all devices
• Clearing cache and cookies multiple times
• Reinstalling Microsoft Authenticator multiple times
• Removing 2-step verification where possible

I was able to sign into Microsoft 365 (admin center / web apps) with alternative email using “Sign in another way” options, but I am still unable to access Outlook (desktop and mobile) — which is the main goal. In Microsoft additional security options - changed some settings.

I removed two-step verification because Outlook keeps prompting for approval through the Microsoft Authenticator app. Authenticator app does not let me add my work account it is showing an error. Thus unable to approve the code in the authenticator app, stuck in the loop. When I removed two-step verification in Microsoft additional security options, signed out of all the devices, cleared cache and cookies, attempted to sign in again, being prompted to enter backup email for the verification code, which is not being sent after numerous attempts while I received notifications to that email that two-step verification was removed. Stuck. Any tips would be great. Thank you!