Backfaces always appear transparent. Is it possible to display them in black or another color? Different from the color of the front faces, of course.
Turn on Face orientation is not an option, as it fills up front faces too.
Blender Stack Exchange is a question and answer site for people who use Blender to create 3D graphics, animations, or games. It only takes a minute to sign up.Sign up to join this community
You can use Geometry node's Backfacing output to mix different shaders. If it's only for preview you can set up different outputs for Cycles and EEVEE. You can set it up so it only works with EEVEE(that is what you get while in LookDev mode), but will not be rendered with Cycles.