It’s not entirely clear from the post, but allow me to provide some further context as I received this same pop-up myself.

I had purchased a legit Windows 10 Pro license with my own money for a custom built PC. Was always a trim installation because that’s how I roll. Still got this out of nowhere when I booted back into my Windows partition the other day, was unclear what app or process pushed it. Some update either added a new app responsible for pushing these desktop level ads or enabled a pre-existing notification feature I had previously disabled. Just a typical Win10 toast notification a few moments after logging in. Dismissed it quickly and did not care to investigate, but that’s about as bad as you can really get, IMHO. They’ve slowly been pushing the bounds, but here we are: ads straight to the desktop.