Any Android TV device using a non-default launcher has no ads whatsoever, and you can just download one off the Play Store.
That's what I did when my Shield TVs received the Google TV-like UI update, and what I did for my parents on their Chromecast w/ Google TV.
If I pay for something, I'm not going to accept any kind of advertising on it. I paid for it, I'm not going to keep paying for it for all eternity by looking at ads.
If there is no option for no ads, then you won't get a cent of my money. I wouldn't accept ads if they were actively, continuously paying me for seeing them.