This is the only open source one:
It even has a very fast workflow (with the few tools)
But I don’t want to miss saying that these blender addons can do more (together with blender):
and there are a few other helpers (simpler addons).
I am e.g. happier with blender_paint_layers together with grungit.
But with “procedural” something has been going on for some time:
This is my favorite (it’s the fastest procedural texture workflow i know)
Edit : It is better to use Chromium instead of Firefox (problems with fly-out menu) Works great with Dark Reader