I know this is an old post, but for anyone else who reads this in future:
My quick testing of DS4K on an Ultrawide monitor it does "work" it's just that it seems to use the central 16:9 shaped part of the video output to determine what colours to output. So if you have say a red image on the whole right half of the screen the lights on the right will be red. But if you have red on the middle of the screen and green on the edge then the lights on the right will likely be red, not green.
So it's not useless in an Ultrawide setup, just not ideal/accurate.