Many folks who ferment though use a mix of whole grains, like wheat and oats.
I tried fermenting their crumbles once and it's just a big mash. I had Kalmbach's Henhouse Reserve here as their scratch, so for years now I make up a mix of half of that, then equal parts of each of whole red winter wheat and whole oats. Mix those three things up, fill a quart jar half full, then I mix in a tablespoon of Chia seeds and whole flax (more than that makes it gummy). Add water to nearly the top and stir; cover with cheesecloth or the like so it can breathe. Keep a layer of water on top so it doesn't mold, and stir every day until the 4th day. Drain and serve.