Designed for Android 4.0 (Ice Cream Sandwich) and above.

Smart YouTube TV 6.17.391: Why Upgrading Makes Your Smart TV Experience Better

If you are looking to set this up or fix a broken version, the community consensus is to avoid sketchy third-party "story" sites and go directly to the source: Official Source

As it is not available on the Google Play Store, it must be side-loaded.

No. Smart YouTube TV is a completely separate application and does not integrate with YouTube Premium subscriptions. However, since the app already provides ad-free viewing and background playback for free, most Premium subscribers find they no longer need their subscription when using Smart YouTube TV.

Version 617.391 was released before the developer felt pressured to fully integrate the "Shorts" shelf into the home UI. In later builds (specifically 625+), you cannot fully disable the Shorts row without editing compiled XML files.