Krita

Krita was written by and for people who paint, and it shows in the brush engines. You can dig into how a brush spreads, smudges and reacts to pen pressure at a level of detail most apps never expose, and the stabiliser is good enough that shaky line art stops being an excuse. There is an animation timeline too, which makes it one of the few free tools where you can rough out a short loop without leaving the app.

Nothing is behind a payment. The $12.99 Mac App Store listing is the project's tip jar with automatic updates attached, and the free download from krita.org is the same program. If you want to support the developers, buy it there; if you want to try it first, just download it.

Where it gets uncomfortable is the Mac side. The macOS builds have lagged Windows and Linux for years on speed and on tablet quirks, so plug in your Wacom or Huion and draw for half an hour before you trust it with paid work.

Do not come to Krita for photo retouching, page layout or vector logo work — that is Inkscape, Affinity or GIMP territory. And if you are already comfortable in Procreate on an iPad, Krita on a Mac will feel like a different job rather than an upgrade.