Cook sausage and red pepper flakes in a Dutch oven over medium-high heat until crumbly, browned, and no longer pink. 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. (We made without bacon and it was still delicious) Stir in the onions and garlic and cook until onions are soft and translucent, about 5 minutes.
Pour the chicken broth into the Dutch oven with the bacon and onion mixture and bring to a boil over high heat.
Add potatoes, and boil until fork tender, about 20 minutes. Reduce heat to medium and stir in heavy cream and cooked sausage. Heat through. Mix spinach into soup just before serving.