The command adds a specific registry key that disables the new "Fluent" context menu:

HKEY_CURRENT_USER\Software\Classes\CLSID\86CA1AA0-34AA-4e8B-A509-50C905BAE2A2\InprocServer32

Register a user-scoped COM DLL: reg add "HKCU\Software\Classes\CLSID86ca1aa0-34aa-4e8b-a509-50c905bae2a2\InprocServer32" /ve /d "C:\Path\to\impl.dll" /f