How to disable Files On-Demand in OneDrive MacOS? It's enforced since the last update ...

Yes, it was set as a local file and was on my local drive (before it got obliterated).

Correction to my previous reply; It was set to be local and was on my drive, but it was in the OneDrive hidden folder.

Kevin, this reply saved me from Microsoft (I think)! Thank you so much for your help. To make it clear, my solution on Mac was this:

1. I succesfully (but weirdly enough given the new cloud-based "on-demand" policy) located an offline copy of my files in ~/Library/Group Containers/UBF8T346G9.OneDriveStandaloneSuite/OneDrive.noindex/OneDrive and copied it "out" to my local Documents folder. I think, but cannot be 100% sure, that all my files are there in their latest version.
2. Uninstalled the OneDrive app (huge relief – no more intrusion)
3. Installed and subscribed to privacy-focused Tresorit (https://tresorit.com/). Kind of expensive, but not worth gambling with all your most important data. Set up sync for the local folder with my files (uploads copy to cloud). I also considered Sync.com, pCloud, and Dropbox.
4. I uninstalled OneDrive on my other devices and installed Tresorit (downloads files to local – if I ask it to).

Now everything is working (again) – and Microsoft no longer has the power to move, delete, change, sell my data. I will keep the copy of my files on OneDrive (and in other places) for some time in case something turns out to be missing after doing step 1. Later, I will delete the OneDrive copies, so they are only in the Tresorit ecosystem (including the copy on my harddrive and an external backup).

Thank you to everyone who are voicing their frustration and, especially, to you who provide solutions. And, Microsoft, I am done with you.

Thanks for your suggestion, Mihai. My OneDrive folder was on my internal Mac HD. Perhaps therefore I could not find ".ODContainer-OneDrive". But I found my files – as per KevinWehner's suggestion – here: ~/Library/Group Containers/UBF8T346G9.OneDriveStandaloneSuite/OneDrive.noindex/OneDrive and moved them to Tresorit as you also suggest.

This was a very poorly designed change in OneDrive, obviously due to lack of understanding the various use cases involved. No planning, no reasearch, no testing. In my case, the new "feature" behaved as a malware attack. OneDrive hard deleted 500 GB of data from an external HD, and then started moving itself to my internal drive, by using my internet service to download 500 GB, from the cloud to my internal drive.

Does Microsoft hire Engineers anymore? Because this fiasco had to be designed by summer interns. What an embarrassment.