Why cannot watch Apple TV on LG Smart TV - newest model

What exact model TV? Is your model TV listed as compatible with the Apple TV app? Are you able to find or download the Apple TV app among your smart apps?

Did you redeem the offer for Apple TV+ on your iPhone first? The subscription is not automatic. Users have to accept the offer and sign up for it.

Once that is done, you may open the app, and sign in to the app with your Apple ID account.

Once signed in, all the Apple TV+ content should be unlocked to subscribers.

if your model on the list of apple tv app enabled models? Apple TV app - Devices - Apple

if so have you read Watch on LG Smart TVs - Apple Support