Can't log into halo mcc on steam due to authentication app

If only your old number appears there, and any other methods, click on I don't have any of these.

It will prompt you to a recover form. That should help you.

Grayson, if you tried to log in to your account. It prompts you this screen, right?

No other options

Can't get it on a new phone because the old nu,ber is completely disconnected

Grayson, what's the exact screen you're stuck in?

Oh I see, yes, I'm afraid there's no option to skip it due to the 2fa being a security protocol, that you activate in order to protect your account. :/

And I see. But, that's odd, even reinstalling the game, it doesn't give you the option to log in again with a different account.

Try this Grayson:

Open the Xbox game bar (windows + G) > Settings > Accounts > find your account linked to Steam there, and click unlink > Open the game, and it should ask you to log in again. That should do the trick.