Heat olive oil in a large soup pot over medium heat. Add ground turkey sausage and cook, breaking it apart with a spoon, until browned and cooked through. Drain any excess fat if needed.
Add diced onion, garlic, and celery to the pot. Sauté for 5 minutes, until softened. Stir in tomato paste, crushed red pepper flakes, and Italian seasoning, and cook for another 1 minute until fragrant.
Pour in the diced tomatoes and 6 cups of stock. Bring to a simmer.
Stir in the broken lasagna noodles and cook uncovered for 10–12 minutes, until the noodles are tender. Add more stock as needed if the soup thickens too much.
Stir in the spinach (or kale). Simmer for another 2–3 minutes, until warmed through and the greens are wilted.
Taste and season with salt and black pepper as needed.
Ladle into bowls and top with grated Parmesan and a small scoop of ricotta.