how to enable "nearest neighbour" scaling algorithm for non-native resolutions in linux?
also known as "pixel doubling" for (for example) when 4K screen is set to use 1920x1080 resolution.
see here for more detailed description (as well as a link to xrandr patch that was supposed to make it easy but seems to be rejected for unclear reasons):
the goal is to get rid of blur that occurs whenever desktop resolution is smaller than monitor's "native" resolution