Start by browning the ground beef in a large skillet over medium-high heat, then drain off any excess grease. Transfer the cooked ground beef to a 6-quart crockpot. Add the diced onion and red bell pepper, followed by the crushed tomatoes and petite diced tomatoes. Stir in the Italian seasoning and minced garlic. Pour in the beef broth and mix to combine. Cover the crockpot and cook on low for 6 to 8 hours or on high for 3 to 4 hours. After the initial cooking time, remove the lid and break the lasagna noodles into bite-sized pieces, adding them directly into the crockpot so any small fragments fall right in. Stir to combine. Cover again and cook on high for an additional 30 to 45 minutes, or until the noodles are fully cooked and tender. Ladle the soup into bowls and top each serving with a spoonful of ricotta cheese, a generous sprinkle of shredded mozzarella, and a handful of grated Parmesan cheese.