Squares 1 through 4 are indistinguishable from the background on Lagom's Black level test.
I have used the sRGB mode with no calibration to test it. I also have used AdobeRGB mode + calibration using a Spyder5Pro with DisplayCAL. Both configurations failed the Black level test.
I used the black level setting on the monitor and that fixed the black level, but it made the monitor fail the white saturation test, so the Black level setting merely pushed all of the values up.
If it helps to debug, the DisplayCAL calibration looks exactly the same as the sRGB setting on the monitor, however there is an unnoticeable difference in green levels (because the program had me adjust the green output using RGB sliders on the monitor).
How do I pass the Black level test with this monitor? My photo editing thought process changes from time to time, sometimes focusing on color saturation, sometimes luminance of the subject (relative to pure white) and sometimes luminance relative to pure black. This causes issues with getting a consistent idea of where I need to adjust the image exposure to.
Sorry to hear about that! What cable are you using, and are any adapters being used? You may need to adjust the HDMI RGB PC Range on the monitor, as that would account for this (default is 16-235, but it typically needs to be on 0-255)