Windows 11 or Onedrive has moved all my files into Onedrive. What is going on?

"So here is my supposition: OneDrive, by default, at some update in the last few months, automatically turned on SYNC, and my Documents folder (and Pictures and Desktop) all got moved to OneDrive folders.

I since then, used the info here to turn off the sync of these folders. But that did not move them back, so they continued to live in OneDrive and continued to sync."

Yes. The OneDrive folder is always there even when you uninstall OneDrive. However, if OneDrive is uninstalled, then it no longer syncs to the online OneDrive.

"PS - I am assuming that if you turn sync on, it moves those folders from the username folder to the OneDrive folder."

Yes, that's right. There is no problem leaving them in the OneDrive folder unless they start syncing again.

"But if you turn sync off, it does nothing, as it does not move the folders back again. And the only thing that will sync in OneDrive, are the actual folders and files in the OneDrive folder structure. Hence why you have to manually move the folders back again."

Yes

To stop the "Sync and Backup" of your folders, go to Manage Backup in the OneDrive Settings. In Windows 11, you will find Manage Backup at OneDrive Settings > Sync and Backup tab > Manage Backup.

"C:>Users>username>ManilaFolders" is a good location on the C drive to hide data from OneDrive**.** An external drive and a separate data partition are great ways to avoid OneDrive.

Create and format a data partition

If sync turns on by itself or OneDrive reinstalls without asking, you may want to avoid the Documents folder and the other standard folders.

A YouTube video explaining more about this is here: https://www.youtube.com/watch?v=3yXgyrsqraE