LG TV models from 2016 or later (webOS version of 3.0 or newer) should be able to install the Apple TV app, through the on-device Content Store. Unfortunately, older models than that wouldn’t be supported for this.
Users with unsupported TVs may consider getting a supported external HDMI streaming device to access the Apple TV app through there. That can be an Apple TV box, Roku, Fire TV, PlayStation (4, 5), Xbox (One, One S, X, S), ‘Chromecast with Google TV’-dongle, or Nvidia Shield TV. Select external TV-provider cable boxes or satellite TV boxes (TV-tuners) that support apps may also support the Apple TV app.
Lastly, with a proper HDMI adapter, you may connect your iPhone, iPad, Mac or PC directly wired to a TV, to watch on the bigger screen that way. Not as convenient, but supported.
All the ways to watch Apple TV+ and more - Apple Support
Get the Apple TV app on your smart TV or streaming device - Apple Support
Watch on these smart TVs and third party streaming devices - Apple Support