I would appreciate a link to the details about 'setting a flag.' The last version of that I used earlier this year stopped working in recent months, and I believe I saw tech news stories to the effect that Microsoft had intentionally closed that path.

For now I just use a customer-supplied email address which I used to setup a Microsoft account, setup Windows and use that account, immediately create a local-only 'admin' account with full rights, delete the online associated account, and start creating user account(s) from there.