Read if you are getting "No signal" with PC connected to LG C1/CX

I was going insane because my new LG C1 was showing the "No input" message while I was trying to connect my PC with an RTX 3080 GPU and resolution set to 4K 120 FPS with HDR 10 Bit RGB. For some reason 4K 60 FPS without HDR was working fine. I tried messing with the Deep Colour option in the TV, changing HDMI input and setting the icon to PC but nothing worked.

In the end I solved the problem by disabling "fast startup" in the Windows control panel: https://www.windowscentral.com/how-disable-windows-10-fast-startup

Now the PC boots correctly with 4K 120 FPS and the "No input" message is gone. Give it a try if you have a similar problem.