HelloThank you for posting in Q&A forum.
You can set a default domain for logon using Group Policy Objects (GPO).
Navigate to Computer Configuration > Administrative Templates > System > Logon.
In the right pane, find and double-click on Assign a default domain for logon.
Set the policy to Enabled.
Under Options, enter the name of the domain you want to set as the default.
Reference:
Use GPOs to change default logon domain name - Windows Server | Microsoft Learn
I hope the information above is helpful.
If you have any questions or concerns, please feel free to let us know.
Best Regards,
Daisy Zhou
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