LG and Apple have started rolling out the Apple TV app on 2018 LG models. The app offers access to iTunes movies, Apple TV+, and 'channels'.
Apple TV app
After 2019 and 2020 LG TVs, the app has started rolling out on 2018 LG models in Europe, USA, and possibly other regions. There are multiple reports on social media and FlatpanelsHD has been tipped by owners who now see the app.
The Apple TV app offers access to iTunes movies (rentals/purchases), Apple TV+, and 'channels' from partners. It supports 4K resolution, Dolby Vision, and Dolby Atmos on LG 2018 models, according to users.

It is a little unclear if the app has been enabled with the latest firmware update or if it can be installed from the app store without further ado. If you are not seeing it in the app store, try updating the firmware of your 2018 LG TV to 05.20.01 (B8 and LCD models) or 05.20.02 (C8 and other OLED models) via the built-in update function or manually with the download files on the support pages on LG USA or LG Europe.
The Apple TV app is also available on Apple TV HD/4K, select Samsung TVs, select Roku devices, select Amazon FireTV devices, and later select Vizio and Sony TVs.
Also read: List: TVs with Apple TV app, Apple TV+, AirPlay 2 & HomeKit
LG will also add AirPlay 2 and HomeKit support to 2018 models via a firmware update scheduled for October 2020.