Preheat your oven to 400°F (200°C).
Lightly grease a large baking dish or oven-safe skillet. Arrange the bell pepper halves cut side up in the dish.
In a large mixing bowl, combine the shredded chicken, mayonnaise, buffalo sauce, garlic powder, onion powder, kosher salt, black pepper, nutritional yeast if using, and sliced green onions. Stir until the mixture is evenly coated and creamy.
Taste the filling and adjust with additional buffalo sauce or salt if desired.
Divide the Buffalo Chicken Stuffed Peppers filling evenly among the prepared pepper halves, gently pressing the mixture into each pepper.
Cover the baking dish tightly with aluminum foil and bake for 30 minutes.
Remove the foil and continue baking for another 20 minutes, or until the peppers are tender and the filling is hot, bubbling, and lightly browned around the edges.
Remove from the oven and let the peppers rest for a few minutes before serving.
Drizzle with dairy free ranch dressing and garnish with additional green onions and fresh herbs before serving.