According to Doug Lynch at xda-developers.com:
Android TV owners recently received an update across multiple platforms that have started to display sponsored content with a "Promotional Channels' title in the launcher of the Android TV software. We're currently seeing reports that it has shown up in Sony smart TVs, the Mi Box 3 from Xiaomi, NVIDIA Shield TV, and others. This has been an incredibly off-putting change for a lot of Android TV users. What makes matters worse is people were unable to disable the ads at first, but Reddit user Felisens seems to have figured out how to disable them.
[...] Update: Google's response
A Google spokesperson gave us the following statement:
Android TV is committed to optimizing and personalizing the entertainment experience at home. As we explore new opportunities to engage the user community, we're running a pilot program to surface sponsored content on the Android TV home screen.
(Score: 2) by NotSanguine on Friday April 05 2019, @05:45PM
Apparently, some TV vendors are using the same functionality, but most seem to allow you do disable it. The Google update stops you from doing so.
According to Ars Technica [arstechnica.com]:
No, no, you're not thinking; you're just being logical. --Niels Bohr