https://www.howtogeek.com/331877/how-to-customize-the-recommendations-row-on-android-tv/

Also not the same as what you're asking for, but you should consider this as well:

https://www.reddit.com/r/bravia/comments/40ozx6/howto_remove_featured_apps_section_and_sony/

In what app do I need to deactivate the notifications for these to disappear?

Buy an AndroidTV device that's not piggybacked into any TV that has shady TOS & that monitor everything you do on/around it..?

I recently found this posted on the Bravia subreddit. Before, I used this and this list to remove useless bloatware. It still blows mind how much shit is installed on these TVs. They'd be a hell of a lot better to navigate if they weren't so bogged down.

You get a Shield TV.

(Seriously, Sony's Android TV implementation is cancer. The only work they've done on it is to close all the loopholes that existed to allow you to disable their awful customization and product placements)