Preheat your oven to 375°F (190°C). Generously grease a 9x13-inch ceramic or glass baking dish with olive oil or butter spray.

Heat 1 tablespoon of olive oil in a large skillet over medium-high heat. Add ground turkey sausage, breaking it up with a wooden spoon into bite-sized crumbles. Add diced onion and red bell pepper. Sauté for 6 to 8 minutes until the sausage is browned and thoroughly cooked through and vegetables are tender. Remove from heat.

Spread the thawed and patted-dry shredded hashbrowns evenly across the bottom of the prepared 9x13 dish. Scatter the cooked sausage, onion, and bell pepper mixture evenly over the potatoes. Sprinkle with 1 cup of the cheddar cheese and half of the green onions.

In a large mixing bowl, vigorously whisk together eggs, whole milk, sour cream, garlic powder, onion powder, smoked paprika, kosher salt, and black pepper until completely smooth and frothy. Pour the egg mixture evenly over the layered hashbrowns and sausage.

Top evenly with the remaining 1/2 cup of sharp cheddar and 1 cup of mozzarella cheese. Bake uncovered at 375°F (190°C) for 40 to 45 minutes, until the center is set and edges are golden brown and bubbling. Let rest for 10 minutes before slicing into neat squares. Garnish with minced fresh chives and sliced green onions.