https://techcrunch.com/2022/09/08/youtube-tv-delivers-5-1-surround-sound-to-apple-tv-and-fire-tv-devices/

YouTube TV announced on Twitter yesterday that it now supports 5.1 audio on Apple TVs and Amazon Fire TV devices. With the update, users can enjoy a movie theater-like experience in their homes. Surround sound is only available on compatible YouTube TV programs, and the feature is free for all subscribers. Note that you need the latest version of the YouTube TV App to access 5.1 audio.

To see which content supports 5.1 surround sound, users can go to player controls, select “More,” find the bug icon, and then look for the Codecs section. If the program supports 5.1 audio, “AC-3 / EAC-3” will be listed.