Running a high dpi monitor and squinting to see FreeCAD GUI? Here is the fix I found.

Tested on FreeCAD-0.21 on Ubuntu 22.04

Create this path and file:

~/.local/share/FreeCAD/Mod/UI-font/InitGui.py

Fill it with this:

from PySide import QtGui
myFont = QtGui.QFont("Ubuntu",14)
QtGui.QApplication.setFont(myFont)