I don't think you are understanding the customer's posts. Therefore, none of the solutions proposed by Intuit staff have worked.

We don't want two-factor authentication. Two-factor authentication is already turned off. We don't want multi-factor authentication, but do not know how to turn it off.

This problem occurs (in my account) only in the browser version, not in the (soon-to-be orphaned) app.

How do we turn off multi-factor authentication, when the two-factor authentication is already turned off? Turning two-factor authentication on, then off again does not work to stop multi-factor authentication.

Quickbooks must stop changing customer's account settings without their permission.