How to reduce the desktop size to create a border around the screen

My monitor (LG 43UD79-B) has a problem: The edges (about 5 pixels) around the screen are extremely hard to see unless you literally look at them from a 0 degree angle.
The monitor does have a overscan feature, but enabling it doesn’t fully solve the problem. The overscan feature takes away way too many pixels (probably about 30 on each side) and in addition to that it only does it for the left and the right edge of the screen. On the top and bottom the issue remains the same. I’ve went through every single setting, but there is nothing that helps…

So since this this issue can’t be fixed on the monitor itself (unless it gets a firmware update, which I doubt), I am looking for a way to fix this in Fedora. I’m using KDE btw.
Any ideas?

Here are some photos: