Lyuma 2D Paper Shader

This feature, "Make 2d", will flatten any material onto a vertical plane, by modifying the shader.

Featured in screenshot: Amanatsu by komado showing Silent's Crosstone, Xiexe's XSToon 3.0.1 and Poiyomi Toon v7.1.53

To access, select all the materials you wish to convert, then use the gear menu to select Make 2d - to switch materials back to 3d mode, select Revert to 3d. It works well when combined with an extremely thick outline with solid color.