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.
After the next to last update I would see them when I accessed an attached USB drive.
Was surprised MS let me uninstall One Drive.
Same here. I've seen Task Bar popups as "Tips, Tricks, and Suggestions" that are really advertisements, but those are easily blocked: How To Stop Popups. Obnoxious feature to be on by default. It isn't the first Microsoft marketing has made the company look stupid.
There is a photo of the ad here (2nd photo down): https://techraptor.net/content/windows-10-now-shows-onedrive-ads-in-the-file-explorer
I get all sorts of advertisements.
Always for porn websites.
I guess they know their audience.