Specific documentation regarding WSUS upgrade for Windows 11 might not be available.
Windows 11 is expected to follow a similar update process as Windows 10. Therefore, you can refer to the Windows 10 documentation and resources related to WSUS to gain insights into the general update and management processes.
It's crucial to stay updated with the latest official documentation from Microsoft as they release Windows 11. I recommend regularly checking the Microsoft Docs website and any other official Microsoft channels for updated information and documentation specific to WSUS and Windows 11.