Just posting a random solution out here I discovered myself in case it is any reference.
Just copy pasting here: The monitor was moved closer to where I am sitting and its high-pitched (probably coil) whining/squealing was rather audible.
It was originally just powered through a power strip (nothing special there). And connected to my desktop GPU via DP. However, I noticed that miraculously, after I connected the monitor to my computer (with USB-A to USB-C, but USB-C to USB-C probably works), the whine stopped. (This USB port is for allowing you to feed data back into the computer when you connect something like a keyboard to the monitor.
Probably something about... closing the ground loop happened. Maybe something like off voltages. Maybe the USB simply allowed the excess something to flow out via a ground. I don't know. But whatever it is, hopefully others will find this solution useful!!!
Now that the whine is gone, I'm so lucky I got this to get fixed and go away. My original plan would have been to open up the monitor and get some type of pastes or poster board putty and stick it on the source of the whine. I only now notice how incredibly annoying it was.
So basically.. the story is that it ''could'' get complicated. But try various ways of connecting and grounding the item, I guess. If I tried to pretend I knew what might be the problem, it's that basically the power input is kind of unbalanced. Let's say too high or too low. And the way the circuit was designed ends up causing some components to just have too much of something dumped on them.
(This sounds like coil whine is bad for the device, but from what I've searched in the past, it's harmless and is a cosmetic/annoyance thing)
And then somehow you can try to let the device ground itself. I dunno.