How to make Dia (which uses X11 / XQuartz) work?
This Q &amp; A helped: Dia command line not working
In short:

Copy the script to avoid MacOS preventing running it because of signature mismatch.

Add these 2 lines just before the exec line:
export DISPLAY=:0           # Fixes the &quot;cannot open display&quot;.
export LANG=&quot;en_US.UTF-8&quot;   # Fixes the annoying Xterm window opening.

exec &quot;$CWD/dia-bin&quot; --integrated


Run it from a command-line (or make a shortcut to taskbar, if you know how)
/Applications/Dia.app/Contents/Resources/bin/dia2