High DPI page suffers from some layout and markup shortcomings:

Sections Environment Variable Reference and Coordinate Systems Reference contain a list of keyword -> explanation, but there's no visual separator between these. Consider using either a table, \section's, or at least making the keyword \b bold.

Section Configuring X11 also contains a sub-section about the QT_USE_PHYSICAL_DPI override. It could be made clearer that this is an environment variable - consider linking to the Reference section below and using \c .

Section Configuring Windows misses a space between "severalDPI Awareness"

General: Consider removing details about Qt 5.