The language settings seems to be not working. Though I already set my Chromecast language, my google account language Chinese. Destiny 2 still displays English. Except from games like Sumurai provides language changing menu item, other games only displays English no matter what device I am playing on. Really need fixing!
Those language settings don't affect the games themselves. I would say no games support all of the languages that the Google products might so you can only change languages in-game on a per-game basis for whichever languages that particular title supports.