Unable to access Azure Portal with personal Microsoft account due to MFA prompt — no verification methods available

I'm trying to access the Azure Portal using my personal Microsoft account (Gmail address), but I'm unable to complete sign-in because of an MFA prompt.

When I sign in at https://portal.azure.com/, I'm asked to approve a request through Microsoft Authenticator or enter a verification code. I don't have access to either method, and selecting "Can't use my app right now" only gives me the option to enter a verification code that I also don't have.

Additional details:

I'm signing in with a personal Microsoft account, not a work or school account.

No organization or tenant name is displayed during sign-in.

Two-step verification is enabled in my Microsoft account security settings, but Microsoft Authenticator is not listed among my available security methods.

Visiting https://aka.ms/mfasetup/ tells me that I can't sign in with a personal account and need to use a work or school account.

When I try to sign up for an Azure free account, Microsoft says I already have an Azure account and that the free account offer is only available to new users.

Choosing either the Pay-As-You-Go subscription option or the option to use an existing subscription leads me back to the same MFA prompt.

I believe I may have used Azure previously, but I cannot currently access the portal to check my subscriptions or account details.

I would like to use Azure for personal learning and hands-on Entra ID and systems administration labs. I would prefer to use the free tier if possible.