If 90% (or more) of my rabbits diet is collected forage or grown grain sprouts (corn, wheat, oats) and they live on the ground, do I need to add minerals?
Rabbits in wire-bottomed hutches are mostly fed pelleted feeds with minerals already added, so without this kind of "complete feed," I would say yes, you need to add minerals. Maybe free choice, the same way you would with other grazing animals, or mixed in with their sprouts.