Sole Azure administrator locked out by MFA (500121) — phone support redirects to website, consumer chat cannot help

I use a personal Microsoft account (Hotmail) to administer my Azure subscription. I am the sole user and administrator.

My personal Microsoft account works:
I can sign in at account.microsoft.com using a passkey or the six-digit code from Microsoft Authenticator.

Azure Portal requests additional MFA and only offers:

• Approve a request in Microsoft Authenticator
• Use a verification code

The approval request does not arrive in Authenticator.
The verification code is rejected with error 500121:

"You didn't enter the expected verification code."

The issue also occurs when signing in without a passkey.

I cannot create an Azure support request because portal sign-in is blocked.
Consumer support chat says Azure is outside its scope.
Danish phone support redirects me to a website, and subsequent calls immediately repeat that referral.

Could a Microsoft moderator help escalate this Azure tenant-access issue to the appropriate support team,
or provide a working support route that does not require signing in to the affected tenant?

I can provide tenant ID, request ID, correlation ID, timestamps and ownership information privately.

Best regards