Try blocking this domain manually and see if it works (it wasn't part of my native lists in my router's adblock)
androidtvwatsonfe-pa.googleapis.com
If you have already set up 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, in its place it shows a dark "Google play, Youtube", and something else that isnt very intrusive).
(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).