Preheat your oven to 350°F (175°C). Grease a 13x9-inch (33x23 cm) baking dish.
In a large pot or Dutch oven, heat the olive oil over medium-high heat. Add the ground beef, Italian sausage, and chopped onion. Cook for 8-10 minutes, breaking up the meat, until it is no longer pink. Stir in the minced garlic and cook for one more minute until fragrant. Drain any excess fat and set the meat mixture aside.
To the same pot, add the sliced mushrooms and cook until tender, about 5 minutes. Stir in the broth, drained sun-dried tomatoes, squeezed spinach, basil, nutmeg, and pepper. Bring the mixture to a simmer and cook for 5 minutes.
Return the cooked meat mixture to the pot. Stir in the marinara sauce and crumbled bacon. The ground meat should reach an internal temperature of 160°F (71°C) to be considered fully cooked.
Spread 1 cup of the sauce in the bottom of the prepared baking dish. Arrange 3 no-cook noodles on top, followed by 2/3 cup of shredded mozzarella cheese. Repeat these layers (sauce, noodles, mozzarella) three more times.
Top the lasagna with the remaining sauce and mozzarella cheese. Sprinkle the crumbled feta cheese evenly over the top.
Cover the dish tightly with aluminum foil. Bake for 40 minutes.
Remove the foil and bake for another 10 minutes, or until the cheese is melted and bubbly and the noodles are tender.
Let the lasagna rest for at least 10 minutes before slicing and serving. This helps the layers set. If desired, sprinkle with grated Parmesan cheese.