DIAGNOSIS: Windows ClearType scaling is not configured for this panel. The subpixel layout needs calibration.
FIX: On Windows, search for 'Adjust ClearType text'. Run the wizard. On the page where you choose the clearest text, select the one that looks sharpest to you. Do not skip steps. Also, in the monitor OSD, go to 'Color' -> 'Sharpness' and set it to 50. 60 is the default but can cause edge artifacts.
IF THAT DIDN'T WORK: Ensure your graphics card output is set to 3840x2160 at 60Hz or 144Hz, not a lower resolution being upscaled. Check in your GPU control panel.
HEADS UP: Using the 'VividPixel' feature above 20 will make text look artificially sharpened and grainy. Keep it off or low for desktop use.