[55UM7300PUA seems to be a 2019 LG smart TV from the UM73 series that supports the Apple TV app and the Apple TV+ app.]
You can use the Apple TV (3rd generation) with any TV that has HDMI-in. As an external HDMI device, it will bypass any smart functionality of the connected TV. The Apple TV box will need input from Wi-Fi or ethernet for internet connectivity. The Apple TV box will need a basic HDMI cable to connect to a screen, such as a TV. Apple TV (3rd generation) needs to be updated to system software version 7.3 or later to have the modern Apple TV app that supports Apple TV+.
Set up your Apple TV (3rd generation) - Apple Support