This is only good for uploading one folder at a time. If the folder contains sub-folders, then I have to create all of the sub-folders, and upload the files to each sub-folder separately. This can be time consuming if there are a lot of subfolders.
I will apologize since I am by no means an expert at all of this, and I see that you have been very careful to try all your options.
The last time I tried to upload a large folder with subfolders to OneDrive was when I sent 50 gb of photos there, by dragging and dropping to the OneDrive folder on my computer. It took over 24 hours to upload, but it did work.
Perhaps some of the more "OneDrive savvy" people on this forum would be able to give more helpful advice. In fact, I may start a thread.