My native resolution is 4096x2160. I wasn’t able to set the resolution to exactly half (2048x1080), looks like my GPU card does not support it. But anyway, I tested with 1920x1080 and the pixels are just too large on the 31 inch display - the fonts look ugly etc. Also I often switch windows from darktable to a file manager etc, so unfortunately this solution is not suitable for me.
FYI I’m using Radeon RX-480 with the AMDGPU-PRO driver.