Heat 1 tablespoon of the olive oil in a large cast iron skillet over medium heat. Add the turkey and break it up with a wooden utensil. Add the fennel seeds, onion powder, red pepper flakes, allspice, ¼ teaspoon salt, and ¼ teaspoon black pepper. Cook, crumbling with a wooden utensil frequently, until the turkey is cooked through, about 8-10 minutes. Remove from heat and stir in the maple syrup. Transfer the meat to a bowl.
Return the skillet to medium heat and add the remaining tablespoon of olive oil. Add the onion, apples, kale, and garlic. Cook, stirring occasionally, until the apples are lightly browned, about 8-10 minutes. Add the sausage back to the skillet and stir to combine. Season to taste with salt and pepper. Serve over cooked millet (if desired).