Krita - Krita is a professional FREE and open source painting program. It is made by artists that want to seaffordable art tools for everyone. Concept art. texture and matte painters, illustrations and comics.
DrawPile - Drawpile is a drawing program that lets you share the canvas with other users in real time.
Procreate - Procreate is the most powerful and intuitive digital illustration App available for iPad®.
PaintTool SAI - Learn to draw in different ways.
Autodesk SketchBook - SketchBook drawing and painting software provides designers, architects, and concept artists the tools to sketch ideas quickly and create beautiful illustrations.
Excalidraw - Excalidraw is a whiteboard tool that lets you easily sketch diagrams that have a hand-drawn feel to them.