The recentish popularity of TouchDesigner has certainly brought with it a lot of interest in node-based editors for graphics. Here's a few open source cross-platform tools that I've used:

Cables.gl @cables_gl https://cables.gl/ ( what I used to make the animation)
Coollab @Coollab https://coollab-art.com/
Material Maker @rodzilla https://www.materialmaker.org/
Pixieditor https://pixieditor.net/
Plugdata/PureData + GEM https://plugdata.org/
Graphite https://www.graphite.art/

Each serves different purposes and does things in different ways. For example, all of the above software can render animations but Graphite and Pixieditor aren't really for live visuals.