Preheat the oven to 425 degrees F (220 degrees C). Place crumbled cornbread into a large bowl. Melt butter in a skillet over medium heat and saute onion, apple, and celery until onion is soft and translucent, about 5 minutes. Add to crumbled cornbread. Season with sage, parsley, rosemary, thyme, marjoram, and salt. Add turkey broth 1 cup at a time and stir after each addition until stuffing is moist. Adjust turkey broth amount to your liking, less if you like the stuffing a little drier or more of you like it more moist. Place stuffing in a large baking pan. Bake in the preheated oven for 45 minutes, turning stuffing over every 20 minutes by scraping the bottom of the pan.