Goxel is an open source voxel modeler.
Ranked in these QuestionsQuestion Ranking
Pro Open source
At least somewhat available for GNU/Linux.
Pro Supports procedural rendering
You can script a build for it to render.
Pro Supports .obj
Pro Available on Android
Pro Exports to PLY format
Pro Available in Debian/Ubuntu repository
If you don't have it installed yet, just enter "sudo apt install goxel && goxel" on the terminal, and you will be running it in a few seconds.
Pro Simple Interface
Pro Available on iOS
Works nicely with Apple Pencil.