[kylealden]

Settings -> Notifications -> "Get tips, tricks, and suggestions as you use Windows" is the main one. If you want to really dial it in you can also disable notifications for individual apps like Office or Edge on that page.

Note that if you're on Insider builds, there have sometimes been build-to-build update issues that reset some settings, which can result in this toggle being reset. IMO that's a serious bug you should report, but (hopefully) wouldn't make it to a stable release.

(disclaimer: MSFT employee on the Edge team)