I have the same with two screens on 144Hz. So the 240Hz is not an issue at all. I can only solve it when i connect 2 screens of different make/model and scale one down to 120Hz or so.
I went for the 4K panel as feature films are not presented at the screen size.
Step 1: I made custom resolution for screen 2, with 143Hz in the second box from above. And Selected CVT - reduced.
Step 2: I did select the settings and assigned it
Step 3: Try to set bit depth to 8-bits but does not allow me. So I can quit already, but thats not an option. But OK i continue. And reboot.
Step 4: Ok with one screen it does not work, I do the second one:
Step 5: After reboot
Then i tried:
142 instead of 143, no change
Until I got back to 1920x1080/60Hz. That worked. But we do not have a 1440/144Hz screen for that I think.
Your last screen shot shows 1080p. The other two were at 1440p. Can you try to make a 142hz display for 1080p? This is absolutely working for me running 1080p.
Understood. I'm not saying it's a solution for everyone...but I wanted to be sure it does work on 1080p. Thank you for confirming this.