Cannot remove broken account from "Accounts used by other apps" in Windows 10
Solution 1:
Many guides online just missed the spot to disconnect it. They all show it under the Email & Accounts only.
From the Settings, rather than using "Email & Accounts" go down by two to "Access work or school." On that screen, you should get a list of the same accounts, but Disconnect is the only option if you click on an account for more details.