I've never seen the office nagging. I've never seen a single ad. Not from first boot that I can recall. There are no ads on my lock screen, there are no ads on my start menu.
The only things I can think of, is that I immediately turned off as many bs anti-privacy type settings as possible when I initially set up the system. I also use glasswire and restrict most things that try to go out without my permission (or anything I don't want to allow in general).
When I fire up my start-menu, I've got it defaulted to pinned tiles, there doesn't even appear to be space for an ad that might be getting blocked on there. There are no ads in the all apps section either.
If you had Windows Spotlight on (like the changing background image for lockscreen), they used to show occasional ads there. It could be they removed that.
I also haven't seem them, but I think they were removed by this tool: https://www.winprivacy.de/english-home/ (PLEASE, please check before downloading, I installed it a year ago or more, back then it was ok, I can't guarantee how it's now).
This disables a lot of tracking, but I assume, also disables ads. (I've seen only 1 ad, and that was for the OneDrive in explorer).
Are those dependent on the OEM? My start menu never had any of that from the first setup. Neither of those are on my system anywhere. The only really super annoying thing on my system has been cortana, being unable to fully remove it.
You are being disingenuous because you are a power user who has admitted to carefully reviewing your settings and running a third party cleaner, but you are acting like you are the kind of standard user we are talking about.
Serious question: where are these ads supposed to be showing?