Apple TV4K
How do I "connect" a TV so my Apple TV remote turns the TV on and off?
Apple TV 4K
Question marked as
Verify that the HDMI-CEC feature is activated on both the TV and the Apple TV.
Control your TV or receiver with your Siri Remote or Apple TV Remote - Apple Support
Your TV may refer to HDMI-CEC with a brand specific marketing name, e.g. ‘BRAVIA Sync’, ‘Anynet+’, ‘SimpLink’, etc.
Apple TV refers to it as ‘Control TVs and Receivers’.