https://www.theverge.com/2017/11/21/16684872/youtube-tv-picture-in-picture-android-oreo-update-play-store-google

One of the bigger additions in Android Oreo was picture-in-picture support, but a new software feature is only as good as the applications that support it. And now, with the release of YouTube TV 1.11 on Android, you’ll be able to use Oreo’s picture-in-picture feature to keep watching shows — even while you’re doing other things that aren’t watching shows, via 9to5Google.

YouTube TV joins the fairly small pantheon of apps that support the feature, which includes the regular YouTube app, Netflix, Chrome, VLC, and Facebook. As a reminder: YouTube TV costs $35 per month, but if picture-in-picture support is a crucial feature for you, it’s so far the only game in town. Rival TV services like Hulu and Sling TV don’t support the feature on Oreo yet.