GIMP
Open Source
GIMP stands for GNU Image Manipulation Program which is an opensource image editor program supporting almost every popular image formats.
MyPaint
Open Source
MyPaint is an easy-to-use painting program which works well with Wacom graphics tablets and other similar devices.
Gimp Paint Studio
Open Source
GIMP Paint Studio is a great pack of designing components like brushes, dynamics, gradient etc.
Krita
Open Source
Krita is a professional free and open source painting program.
Photopea
Free
Photopea is a free online image editor, that runs without plugins. It can both read and save PSD files.
Tux Paint
Open Source
Tux Paint is a raster graphics editor (a program for creating and processing raster graphics) geared towards young children.
Compare Leonardo with alternatives
Compare Gimp Paint Studio and Leonardo and decide which is most suitable for you.