- TeX/LaTeX --- batch/markup driven page layout which can do anything one can put together a TeX macro to achieve (I use it a lot and have written articles for TUGboat on it: https://tug.org/TUGboat/Articles/tb24-2/tb77adams.pdf
- Blender -- 3D modeling
- GraviT --- another vector editor, this is likely the one most like to Affinity Designer (since they were both modeled on Freehand)
- Paint.net
- Pixen
- Inkscape --- straight-forward vector editing
- Seashore --- this is Mac OS UI overlay for GIMP
- Krita --- vector editing with painting features
- Scribus --- page layout
- TeX/LaTeX --- batch/markup driven page layout which can do anything one can put together a TeX macro to achieve (I use it a lot and have written articles for TUGboat on it: https://tug.org/TUGboat/Articles/tb24-2/tb77adams.pdf
- Blender -- 3D modeling
- GraviT --- another vector editor, this is likely the one most like to Affinity Designer (since they were both modeled on Freehand)
- FontForge