Do I Need Internet to Use Android TV / Google TV?

No. but internet is required for full smart features

What Works WITHOUT Internet

You can still use your TV as a normal TV:

• Watch free-to-air channels (via antenna or Satellite） 
• Play media via USB (movies, photos, music)
• Use HDMI devices (DVD player, gaming console, set-top box)

The TV will function like a standard non-smart TV

What REQUIRES Internet

To use smart features, you’ll need a connection:

• Streaming apps (Netflix, YouTube, etc.)
• Downloading apps from Google Play Store
• Google features (voice control, recommendations)
• Chromecast / casting from your phone

Without internet, these features will NOT work