While version 6.17.391 remains a "latest exclusive" for very old hardware, the developer has since shifted focus to a successor called (formerly SmartTubeNext).
Smart YouTube TV 6.17.391 (noarch) (Android 4.0+) - APKMirror smart tv youtube 617 391 download latest exclusive
: Users can access their subscriptions and history through an external activation link without requiring Google Play Services to be installed on the TV itself. Download and Installation While version 6
Because this is an independent, third-party client, it is not available on the official Google Play Store. Users typically "side-load" the APK file using the following process: smart tv youtube 617 391 download latest exclusive