colour theory:
Color—the theory and practice of painting [PDF]

drawing:
Summer Drawing Starter Pack [tutorial playlist]
https://line-of-action.com/practice-tools/figure-drawing

painting:
How to Match Any Color with Oil Paint
How to Paint Flesh Colours Using the Zorn Palette

software:
https://www.gimp.org/
https://krita.org/
https://inkscape.org/
https://www.darktable.org/

book:
The War of Art [audio]

Just wanted to say it's a nice initiative!

BTW I stumbled upon this place because the creator (hilliard) responded to one of my comments with "judges you in Zorn", but the thread was deleted and I have no idea what my comment was 😅

Anything being done?

An interesting article in today's Guardian on a new book that re examines his rather dubious reputation....

....driven by all the new material that began appearing in 2019, which coincided with the reopening of the debate about Gauguin’s troubling reputation. It seemed important to re-examine his life: not to condemn, not to excuse, but simply to shed new light on the man and the myth.

edit- fixed link

a history: https://kristenroos.ca/timeline
PyDPainter: https://pydpainter.org/ [modern version of DPaint]
MacPaint Simulator [web]
https://ztoz.blog/posts/macpaint-source-code/