GIMP
Open Source
GIMP stands for GNU Image Manipulation Program which is an opensource image editor program supporting almost every popular image formats.
Photopea
Free
Photopea is a free online image editor, that runs without plugins. It can both read and save PSD files.
LibreCAD
Open Source
LibreCAD is a free Computer-aided design (CAD) application for 2D design. It works on Linux, OS X, Unix and Windows operating systems.
Gimp Paint Studio
Open Source
GIMP Paint Studio is a great pack of designing components like brushes, dynamics, gradient etc.
Compare SketchPort with alternatives
Compare LibreCAD and SketchPort and decide which is most suitable for you.
Compare Photopea and SketchPort and decide which is most suitable for you.
Compare Gimp Paint Studio and SketchPort and decide which is most suitable for you.