If you want to use the Assistant, the microphone which is present on the controller is not that good, so we suggest using the app from your smartphone. On the first boot after installing the update you will see this feature though it could also require latest Google app version.
The Nexus Player was launched in November 2014 with 5.0 as the first Android TV device. It has continued to receive platform updates, and received a completely new interface in September with the launch of Oreo, though it has been excluded from the Developer Preview for 8.1. Conspicuously, the Nexus Player is completely absent from Google's list of support dates for Nexus and Pixel products.