When I bought the Samsung Q9FN flagship TV the last thing I expected was for there to be adverts built into the menu bar, and for movie trailers to start playing when I powered on the TV each time!
For the adverts in the menu bar, take a look in Settings & check the Policy Agreements. Be sure to un-tick any of the options that agree to advertising or tracking. Once you’ve made those changes, the ads should disappear.
The film trailers are coming from built-in apps like TV Plus & Rakuten. It’s not that easy to figure out how to get rid of them; you certainly can’t uninstall the apps.. Samsung don’t let you do that. They’re like the apps that are pre-installed on smartphones.. most of those you can’t remove either.
There’s apparently a maintenance menu that allows you to disable TV Plus, but the jury is out on whether accessing this service menu voids your warranty. There’s an easier way, which I demonstrate in this video, which definitely doesn’t affect your warranty.