Windows veteran Gustave Monce has managed to sideload a (somewhat) working version of Windows 11 onto the Microsoft Surface Duo. The build is quite unstable but works to a certain degree. He plans to sideload Windows 10X onto the foldable smartphone soon.
https://www.notebookcheck.net/Intrepid-developer-successfully-boots-Windows-11-on-the-Microsoft-Surface-Duo.597457.0.html