
Moving known folders to personal OneDrive accounts is already blocked on domain-joined PCs.
If you enable this setting, users aren't prompted with a window to protect their important folders, and the Manage backup command is disabled. If the users have already moved their known folders, the files in those folders will remain in OneDrive. To redirect the known folders back to the user's device, select No. This setting doesn't take effect if you've enabled Prompt users to move Windows known folders to OneDrive or Silently move Windows known folders to OneDrive.
If you disable or don't configure this setting, users can choose to move their known folders.
Enabling this policy sets the following registry key value to 1:
[HKLM\SOFTWARE\Policies\Microsoft\OneDrive]"KFMBlockOptIn"=dword:00000001
To redirect the known folders back to the user's device and enable this policy, set the following registry key value to 2:
[HKLM\SOFTWARE\Policies\Microsoft\OneDrive]"KFMBlockOptIn"=dword:00000002