Hi Klob-Jorkan,
Thank you for posting in the Microsoft Community Forum.
Local Users and Groups are outdated and don't work properly, if you want to set an admin password, you can try setting a local admin password. Here are the steps on how to do it:
Log in to the server: Log in to Windows Server 2019 with domain administrator privileges.
Open Computer Management: You can do this by pressing Win + X keys, then selecting "Computer Management," or by navigating to "Administrative Tools" in the Control Panel, and then selecting "Computer Management."
Select Local Users and Groups: In Computer Management, navigate to "Local Users and Groups" > "Users."
Change the Administrator Password: Right-click on the "Administrator" user, select "Set Password," and then follow the prompts to set a new local administrator password.
Log out or restart: Once done, log out the current user or restart the computer to apply the changes.
Now, you can log in to the Windows Server 2019 client using the set local administrator password without needing domain user credentials. Note that this only affects local user logins and does not impact domain user logins.
Best regards
Neuvi Jiang