Google TV apps were build on Android TV SDK, which is Java/Kotlin-based. Whereas, Samsung uses Tizen (HTML5/JS) and LG runs on webOS (also HTML5/JS). So, you have to build the separate codebases for each platform. Unfortunately, the Google TV guidelines and UI components won't directly translate to Tizen or webOS due to different runtime environments, design standards, and APIs.
However the good news is:
Your backend logic (APIs, video streams, etc.) can remain the same across platforms.
You can follow a modular approach separating frontend UI logic from core business logic to minimize duplication.
There are some cross-platform frameworks (like React Native for TV or Flutter with custom rendering) but support is limited and usually not production-ready for Samsung/LG.
If you're looking for scale and faster deployment, many businesses go with white-label solutions like VPlayed**, Zapp, or Accedo**, which offer multi-platform Smart TV apps with a unified backend and consistent UX. For more details on accessing a while label cloud tv platform checkout: https://www.vplayed.com/cloud-tv-platform.php
In short yes, separate codebases are required but the strategy you use can save you a lot of time in the long run.