Turned mine off by removing ‘One Drive” from ‘programs and features’.
Very easy to do.
Drove me crazy for a while, was installed in an update.
I still have One Drive on my Windows 10 PC and I've yet to see a single advertisement in Windows File Explorer, or any other part of Windows 10. I've no idea what people are talking about when they say they see ads in Windows 10...... I don't see any and to the best of my knowledge I've not done anything special on my pc to disable them.