Same dissapointment here, looks like samsung added useless Ambient display but no way to DIM off screen. - and long pressing Ambient display button might easily turn off screen.
Will not recommend or buy Samsung TV anymore. (Until Samsung cannot implement such mini feature)
I am also developer, and there is even no programatic way how to turn off screen OFF so apps would be able to do so - like Spotify.
I'm am very disappointed and confused too. I've bought QE49Q6FN and there is no "PICTURE OFF" in menu
WHY??? I want to listen to TV broadcast when going to sleep but now I cannot fall to sleep because of shining QLED panel!
Found a solution!! At least for those using Apple TV...
A Samsung is NOT listening to customers needs, I figured out a solution that is giving me, finally, a total black (like an off screen) when listening to music over my Apple TV 4K. What I did is pretty simple: selected Pictures as the screen saver (instead of Aereo or other fancy options). Created a pictures folder with only one picture, which happens to be a total back image. The screen saver displays only that image and voila! I finally have the screen off, or almost off, which only illuminates for a couple of seconds to display song/artist name each time a new song starts, which is fine with me. Hope others find this tip useful.
I eventually used a similar solution. I configured my satellite box to switch on every morning to a local radio station solving my alarm function. Being a linux based satellite box I was able to edit the radio background image so it only displayed a black screen. If Samsung ever bothered to listen to their customers, I shouldn't have to do all this. Of course, Samsung have already gotten their large price from me so no longer give a darn. Unless Samsung rectify this, they will never get any more purchases from me. It should also be remembered that "word of mouth" is a powerful form of advertising.