While finding the Github, I see they now actually package an Electron application, so that is probably worth exploring[2].
[0] https://www.drawio.com/
[1] https://github.com/jgraph/drawio
[2] https://github.com/jgraph/drawio-desktop
The tool is quite basic, until you realize, you can create reusable blocks (in scratchpad) with predifened style.
From that point on you just publish editable PNGs to git and draw them rather quickly by dropping in predefined blocks.
While finding the Github, I see they now actually package an Electron application, so that is probably worth exploring[2].
[0] https://www.drawio.com/
[1] https://github.com/jgraph/drawio
[2] https://github.com/jgraph/drawio-desktop