Some other ones to add on from my fresh install: Start menu search will search the Microsoft Store for apps they want you to install, some key combinations will launch copilot and if it's not setup it will take you to a webpage that will help you set it up, every office application has a cheap looking unhideable jeweled title bar button to "Upgrade your plan".

Solutions in order of the problems listed: https://superuser.com/questions/1927207/how-to-remove-the-st..., https://github.com/midrare/hyperenable, and my favorite: downgrade to a previous version of office which is almost certainly unsafe and has active exploits (16.0.19929.20106). But I hate that button THAT much and my wife refuses to move off of Onenote for our family knowledge management. I am close to just using Onenote in a browser (where I can zap the offending element) but the loading pages on demand is annoying.