Hello
Exactly the same happens to me, I am testing librelec on my Raspberry Pi 4b 4gb on a samsung 4k TV, all menus work perfect, I have tried several resolutions but it does not play the video, the sound does work but the image looks black screen.
Could you solve it?
Previously I had the sd raspbian and if it worked
I hope you can help me, thank you very much in advance.