YouTube finally supports the new 2018 iPad Pros
The App Store description doesn’t mention it but it does, however the iPad’s bar (the one you swipe for home gestures and so) seems to be overlapping the navigation buttons (Home, Subscriptions…)
Edit: I speculate it also supports the Xr and Xs Max? I think I read those devices weren’t supported either but I may be wrong.
Also, iPad Pros support HDR, but apparently the app doesn’t enable it yet.