Posted by Gary S on Sep 15, 2020; 9:34pm
URL: https://forum.librecad.org/Screen-resolution-on-with-4k-laptop-and-second-full-Hd-screen-problem-tp5719542p5719546.html

Also try at the command prompt:
    QT_SCALE_FACTOR=1.5 ./librecad &

The value can be adjusted as required.  0.5 was way too small.  1.0 was the normal scale, 2.0 was too big (icons).   1.5 was just right on a 4k monitor.  Just to be clear - that is the only command that needs to be used.

QT_AUTO_SCREEN_SCALE_FACTOR=  only accepts a value of is 0 or 1 (boolean).  For me, it resulted in something similar to QT_SCALE_FACTOR=2, which resulted in icons that were too large.