(On the shield 2019) If you block this domain with your dns ad blocker, the default launcher will only show ads for the YouTube, Google TV, and Google Play Store apps (not individual shows). I find these to be far less annoying as they use muted tones.
androidtvwatsonfe-pa.googleapis.com
If you have already setup your device and currently see ads, you need to reset the android tv home application data to get rid of them. This will temporarily show you the old dashboard, but the new one will load eventually (without ads).
It's so useful you see it mentioned on every other thread