If you have problems with using Miracast on the LG 4K TV with your Microsoft Surface, you can add the Belkin Miracast Adapter to one of the HDMI ports of your LG 4K Ultra HD Smart TV with webOS 2.0.
Make sure you select correct HDMI input connected to the Belkin Adapter in the TV's input mode and you should be able to see the Belkin startup screens.
Next, go to the Display Settings on your Microsoft Surface and click on "Connect to a wireless display".
Select the LG TV icon that should show up on the right side of your screen and the Surface will start to connect to the Belkin Miracast.
Once successful, the LG TV will show that the Surface is connected and you should be able to see the Surface screen on the TV.
A drag issue was seen where the TV was displaying a screen that was almost half a second late than what was being displayed on the Microsoft Surface 3. We also saw several gliches where you could see the screen becoming blurred and the audio not being in sync with the video. However, this type of lagging behavior is often seen with Miracast. In general, it's recommended to use Miracast only for simple desktop use, browsing, and casual videos and not for high resolution movies and action games.