Here's the response I got from the StackOverflow question from a member of Google's Developer Relations team:
""" Internationalization in the Data API v3 is something YT started supporting recently, and it's limited now. But there is a work going on to bring this support to the all functionalities in the API really soon. """ So it isn't clear how we can progress on this until something changes in the API. I'm lowering the importance to take this into account. Please change it again if you disagree. ** Changed in: unity-scope-youtube (Ubuntu) Importance: High => Medium -- You received this bug notification because you are a member of Ubuntu Touch seeded packages, which is subscribed to unity8 in Ubuntu. https://bugs.launchpad.net/bugs/1359153 Title: YouTube labels and categories are not localized Status in Ubuntu Rest Scopes: Invalid Status in Ubuntu Translations: Triaged Status in “unity-scope-youtube” package in Ubuntu: Triaged Status in “unity8” package in Ubuntu: Invalid Bug description: YouTube scope shows untranslated categories and labels. Test case. - Switch Ubuntu Phone to Spanish, reboot. - Go to YouTube scope. Expected result. - Labels and categories must be displayed in Spanish. Actual result. - "Best of YouTube" and its categories are displayed in English. - "Sports", "Gaming", number of "views" and other labels are displayed also in English. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu-rest-scopes/+bug/1359153/+subscriptions -- Mailing list: https://launchpad.net/~touch-packages Post to : touch-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~touch-packages More help : https://help.launchpad.net/ListHelp