These work fine on AndroidTV as far as being recognized as controllers by Android and being able to use it to control the UI and using it in Android games.

However, on my shield it does NOT work for Gamestream and GRID games, which is really disappointing, hoping Nvidia fixes this.

EDIT: Found this link on another thread talking about controllers: https://forums.geforce.com/default/topic/846052/360-controller-still-does-not-function-in-steam-games-via-geforce-pc-games-app-streaming/#4573458