Use "Option 5" in this tutorial to enable the built-in administrator.
https://www.elevenforum.com/t/enable-or-disable...
Note:
You may need to use the Windows 11 USB setup disk to carry out those steps.
From another computer, create a Windows 11 USB setup disk. To create one, you'll need a USB stick of 8GB or higher capacity. Note that the contents of the USB stick will be erased during the setup disk creation process.
Download Windows 11 Media Creation Tool (MCT) from:
https://go.microsoft.com/fwlink/?linkid=2156295
Run MCT and create a bootable USB disk.
After creating the USB setup disk, connect it to your computer and boot from it. To do so, you may need to change the boot order in the BIOS/UEFI settings. Consult your system or motherboard manual to learn how to access the UEFI settings for your model.