I've heard that ornamental cabbage/kale can be bitter. I'm interested in using it for food, but I would want to make sauerkraut with it (lacto-fermented ornamental cabbage). Is the bitterness going to be as much of a problem here as it would be with cooked cabbage dishes? I'm thinking maybe the sourness from the lactic acid would overpower the bitterness, or maybe the fermenting would change the bitter flavor to something else—or even complement it.
Apparently, it has been done. According to this website, the flavor will be strong compared to sauerkraut:
The flavor is strong; hard to describe — not just simply more acidic but strong, and the texture is a little tough... I also find that kale ferments accentuate the salty flavor, no matter how carefully I salt and I have no idea why. Mirror this with bold flavors. Ferment kale with lots of garlic, chiles, smoked salts, chipotle, curry or other unflinching spices.
So the proposed solution is to make kale kimchi mixed with other vegetables, or add kale to a normal sauerkraut to dilute the harsh flavor.