Cook the moose sausage and red pepper flakes in a Dutch oven over medium-high heat until crumbly and browned, about 10 to 15 minutes. Drain and set aside. Cook the bacon in the same Dutch oven over medium heat until crisp, about 10 minutes. Drain, leaving a few tablespoons of drippings with the bacon in the bottom of the Dutch oven. Stir in the onion and garlic; cook until onion is soft and translucent, about 5 minutes. Pour the chicken broth into the Dutch oven with bacon and onion mixture; bring to a boil over high heat. Add potatoes and cook for about 10 minutes. Reduce the heat to medium and stir in the cream and sausage; heat through. Mix the spinach into the soup just before serving.