I discovered plotutils lately while learning BRL-CAD, a very old but powerful CAD system. There is a command to export views to UNIX plot files which I did not know up to now. An it seems powerful enough for quite a lot use cases.

The metafile format allows for very flexible, generic 2D drawings whereas gnuplot is specialized to 2D/3D diagrams. BRL-CAD extended it for 3D drawings: https://manned.org/libplot3/ff1ca6c1

I like several things about this discovery: * easy conversion to PNG, SVG * actually an alternative to SVG, using idraw * can directly translate from the PIC language without troff. The PIC mini language is a perfect fit (at least for me) to draw simple graphs, flow charts etc.

Yes, it is old, but sometimes I prefer mature proven UNIX tools to fancy new web based applications with questionable privacy statements.