In a heavy 6 to 8 quart saucepan, cook bacon over medium heat, stirring frequently until browned. Remove with a slotted spoon to plate. Set aside. Pour off all but 2 Tablespoons of the bacon fat, and return the pot to medium heat. Add the onion and celery. Sauté until the vegetables are soft, but not browned, about 3 to 5 minutes.
Add the potatoes, squash, and turkey stock. Bring to a boil, and reduce the heat to a simmer. Partially cover the pot and cook until the potatoes are tender, about 15 minutes. Add the zucchini, Swiss chard (or kale), turkey, sage, thyme, and reserved bacon. Cook 5 minutes longer. Add salt and pepper to taste. Ladle the soup into warmed individual bowls or mugs and serve.