Hi Lillian Kish,
Have you tried to go to Settings => Accounts => Family & other users?
Under “Other users,” choose Add account => “How will this person sign in?”, click I don’t have this person’s sign-in information. On the next screen (“Let’s create your account”), choose to add a user without a Microsoft account. After that, you can enter a username or password
If that option is nor there or gray out, you need to sign in as administrator or use CMD:
net user NewUsername NewPassword /add
Remember to replace NewUsername and NewPassword.
Overall, you must select “Add a user without a Microsoft account” to create a true local “Other User.” The error appears only if you try to use an email not registered as a Microsoft account.
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