Preheat the oven to 350°F (175°C).

Grease a 9×13-inch casserole dish with cooking oil or non-stick spray.

In a Dutch oven, heat a tablespoon of avocado oil over medium heat and sauté onion, green pepper, and sweet potato cubes for about 8-9 minutes. Stir in minced garlic in the last minute.

Spread the sautéed vegetable mixture evenly in the prepared casserole dish.

Cook the turkey sausage in the Dutch oven until fully cooked, about 5-7 minutes, then mix into the vegetable layer in the casserole dish.

In a mixing bowl, whisk together eggs, milk, fresh thyme, salt, pepper, and shredded cheese until smooth.

Pour the egg mixture over the sausage and vegetable layer in the casserole dish and gently stir to combine.

Bake for 40-45 minutes until the center is firm and golden on top. Cover loosely with aluminum foil if browning too quickly.

Let the casserole cool for 15 minutes before slicing.