Heat a large heavy pot over medium heat and add ground beef and chopped onion.
Cook, stirring and breaking up the meat, until beef is browned and onion is softened.
Add minced garlic and cook for about 1 minute until fragrant.
Season with Italian seasoning, salt, and pepper; stir well to combine.
Add marinara sauce and diced tomatoes with their juices; stir everything together.
Pour in broth and bring the mixture to a gentle simmer.
Add broken lasagna noodles to the simmering soup and cook uncovered, stirring occasionally, until noodles are tender, about 10 to 12 minutes.
Turn off the heat and stir in part of the shredded mozzarella and Parmesan cheeses until melted and creamy.
Ladle soup into bowls and top with ricotta dollops if desired, more mozzarella and Parmesan, and garnish with fresh herbs.
Serve immediately while hot, ideally with crusty bread for dipping.