It is a bit more complicated than that. That setting is for the GUI but also sets the output resolution and frame rate of playing video IF you don’t have adjust refresh rate enabled. If you have adjust refresh rate switching enabled then video will be output at the GUI resolution and higher at an optimized frame rate. A whitelist with refresh rate allows for output both above and below the GUI resolution depending on what is set.
If you use the recommended settings your should get HDR output during playback and when the video starts you should see on your LG and black screen followed by a HDR logo in the top right corner display for a couple seconds. If not already enabled on your LG you will have to enable “HDMI ULTRA HD Deep Color” in its menus.
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We recommend people with 4K TV’s set their user interface (UI) to 1080p. Kodi’s UI is not optimized for 4K yet and this can put unnecessary demands on your device and can lead to a suboptimal picture quality, as well as potentially cause other issues.
The settings we recommend are as follows…
Settings>System>Display>Resolution> 1920x1080p
Settings>System>Display>Whitelist> (empty) *
Settings>Player>Videos>Adjust display refresh rate> On start/stop
Some televisions may also need, or benefit from, the following being set…
System>Display>Force 4:2:2 colour subsampling> (enable)
With the above settings your UI will be output in Full HD and your 4K content will be output in 4K. *Information regarding the whitelist can be found here. If you have any doubt, feel free to upload some logs so we can verify that your settings are indeed correct.