Hi Mutant,
I’d try the basics first:
-make sure your AppleTV OS is up to date.
-make sure your LG TV OS is up to date.
-try a different HDMI cable
-try a different HDMI port on the TV (on the TV HDMI ports, certain ports may be labeled as specific feature included).
From poster Urquhart1244 (who is one of the most knowledgeable AppleTV people on the discussions board):
”HDMI-CEC should be activated on both devices for this to work.
- On your TV, look for a “SimpLink” setting, as LG calls it.
- On your Apple TV, look for Settings﹥Remotes and Devices﹥Control TVs and Receivers﹥
Control your TV or receiver with your Siri Remote - Apple Support”