I finally eliminated the terrible judder that I was experiencing with my Samsung 75QN85QNDA QLED. I have been experimenting with different settings. The only thing that works is to have the intelligent mode on and use custom picture clarity settings on auto. If you do this, judder will be undetectable.
I too was having maddening judder issues and tried your technique. It did help somewhat, but it positively did not fix the issue. In my case, I was driving the TV from my computer (and playing movies via VLC) and the Monitors preferences for the TV was set for a frame rate of 60Hz. Changing that to 24Hz (the standard frame rate of motion picture movies) totally fixed the judder issue for me. That being said, it is sad that this advanced TV can't deal with a 60Hz frame rate. I also noticed that 30Hz seemed to work fine, but figured 24Hz was likely the smarter choice given my viewing habits (which is movies and TV shows only).