Heat the olive oil in a large Dutch oven or heavy-bottomed pot over medium-high heat until shimmering. Add diced yellow onion and cook for 5-7 minutes until softened and translucent.
Add lean ground turkey to the pot, breaking it up as it cooks. Cook for 8-10 minutes until fully browned, draining excess fat if necessary.
Stir in minced garlic, diced red and green bell peppers. Cook for 3-5 minutes until peppers soften and garlic is fragrant.
Add chili powder, ground cumin, smoked paprika, dried oregano, and cayenne pepper (if using). Stir and cook for 1 minute to toast the spices.
Pour in crushed tomatoes, tomato sauce, rinsed kidney beans, rinsed black beans, and diced green chilies. Stir to combine.
Add chicken broth and season with salt and black pepper. Stir well to distribute seasoning evenly.
Bring the chili to a gentle boil over medium-high heat. Reduce heat to low, cover the pot, and simmer for at least 30-45 minutes, ideally 1 to 1.5 hours, stirring occasionally.
Taste and adjust seasoning as desired, adding more salt, pepper, or chili powder for extra flavor.
Serve the hot chili in bowls with your choice of optional toppings such as cheddar cheese, Greek yogurt, cilantro, avocado, jalapeƱos, or corn chips.