YouTube Premium receives 1080p offline downloads option, but only on iOS
UPDATE: We've just been tipped by a user from India that the new 1080p option does appear on Android devices as well.
The new feature only appears in India, so it looks like this is a limited roll-out. It's possible that when Google is ready to kick off a broader deployment to add the 1080p option to Android devices as well, but we won't know for sure until more YouTube Premium users are getting the new feature.
It's unclear whether or not YouTube plans to make the new feature available to non-Premium users, but it's highly unlikely. If you live in India and own an iPhone, you should update to version 14.30.6 to get the new offline download quality option, but there's no guarantee that it will be there.
Things that are NOT allowed: