Went round and round on this - now the Samsung is matching my Laptop (MacBook Pro 15 Inch 2018) darned near perfectly.
The trick for me was ditching the U28E590 Profile in Display Settings for the monitor and choosing "Thunderbolt Display". This alone got things very, very close.
Then on the monitor, here are my settings:
Contrast: 100 (...
I went to the Apple store to get some diagnostics done. When I plugged into one of the high end 4K LG monitors that had USB C built in it ran fine, even using Affinity Photo on high resolution projects. My guess is the USB-C adapters I tried were only Thunderbolt 2 and not Thunderbolt 3 capable. The hard part is getting honest/clear specs on the adapters, ...
HDMI 2.0 4K60Hz might use chroma subsampling (YCbCr422 10bpc)
You can force RGB by overriding the EDID (limits you to 8bpc)
DisplayPort 1.2 is preferred because it has slightly more bandwidth ...