Line medium bowls with paper towels and set aside. Heat dutch oven over medium heat.
When pot is warm, add Italian sausage and crushed red pepper flakes. Cook, breaking up pieces of sausage with spoon, until meat is browned and cooked through.
Use slotted spoon to remove sausage from pot, draining any fat, and transfer sausage to one bowl lined with paper towel. Set aside.
Add diced bacon to dutch oven. Cook until bacon is crispy, approximately 5 to 10 minutes, turning pieces as needed to prevent burning.
Use slotted spoon to remove bacon from dutch oven, leaving rendered bacon fat in pot. Transfer cooked bacon to other bowl lined with paper towels. Set aside.
Add chopped onion and minced garlic to dutch oven with rendered bacon fat. Cook, stirring occasionally, until onions are soft and translucent - approximately 5 minutes.
Pour chicken stock into dutch oven and increase heat under pot to high. Scrape up any browned bits stuck to bottom of pot, then bring liquid to boil.
When chicken stock begins to boil, add diced potatoes. Boil potatoes until fork tender, approximately 10 to 20 minutes.
When potatoes are cooked through, reduce heat to medium. Let soup cool slightly, then stir in heavy cream and cooked sausage, until ingredients are well incorporated. Cook over medium heat until warmed through.
Immediately before serving, add cooked bacon and fresh kale to zuppa. Stir to incorporate and cook only until kale is bright green and softened.
Taste zuppa and season with salt and pepper as desired. Serve warm.