Egg Hash Brown Casserole

Name: Egg Hash Brown Casserole
Ingredients: Cooking spray; 1/4 c. extra-virgin olive oil, divided; 1 lb. loose pork or turkey breakfast sausage; 1 medium yellow onion, finely chopped; 1 medium red bell pepper, seeded, finely chopped; Kosher salt; Freshly ground black pepper; 2 cloves garlic, minced; 10 c. (packed) baby spinach (from 2 [5-oz.] containers); 1 (20-oz.) bag frozen shredded hash browns; 8 large eggs; 3/4 c. low-sodium chicken broth; 1/2 c. sour cream; 1 tbsp. Dijon mustard; 1 tsp. hot sauce; 8 oz. shredded cheddar (about 2 c.), divided