How can one change the font size for the menu of mathematica 11.3 under linux? I looked under Core.nb but to be honest its rather above me. I joined a screen to show the problem. Thanks in advance for any helpful advice. :)
A possible solution which worked for me (running Fedora v30) can be found on the Wolfram community forum. There, you want to navigate to the directory containing your Mathematica executable and run:
QT_AUTO_SCREEN_SCALE_FACTOR=1 QT_SCALE_FACTOR=1.33 ./Mathematica &
Depending on your screens resolution you may need to adjust these values. If you're running Ubuntu then this post might be useful.