Brown the sausage in a large skillet over medium heat for about 5–7 minutes, breaking it apart until fully cooked. Remove with a slotted spoon, leaving drippings behind.

Sauté finely chopped onion and diced red bell pepper in the same skillet for about 4–5 minutes until softened. Stir in thawed hash browns and cook until lightly browned, about 5 minutes. Mix the cooked sausage back in and remove from heat.

In a medium bowl, whisk together eggs, whole milk, salt, and pepper until blended and frothy. Set aside.

Preheat the oven to 375°F (190°C). In a 9x13 inch baking dish, spread a thin layer of the egg mixture, layer with lasagna noodles, half of the sausage and vegetable mixture, a generous amount of cheese, and repeat for three layers.

Cover with aluminum foil and bake for 30 minutes. Remove foil and bake uncovered for another 15–20 minutes until cheese is bubbly and center is set.

Let the lasagna rest for about 10 minutes before serving for easier slicing. Serve warm.