The problem is as following: my 4K screen when viewing a HDR video on VLC player or Kodi will only stay in HDR mode if i play the video in windowed mode or ...
VLC HDR settings are turned on by default, if not, you can just open your VLC > Tools > Preferences > Video > choose OpenGL video output for Windows or OpenGL video output from the drop down menu of Output > then, click on Save button