Place a large skillet or Dutch oven over medium heat. Add 1 Tablespoon oil and then add onion, bell pepper, and garlic with a pinch of salt. Saute until very tender, 6 to 7 minutes. Transfer to bowl of a 6-quart slow cooker.
Return pan to heat and add 1 Tablespoon oil. When oil is shimmering, add sausage and saute until browned, 8 to 10 minutes. Add to bowl of slow cooker.
Return pan to heat and add 1 Tablespoon oil. When oil is shimmering, add beef and saute until browned, 8 to 10 minutes. Add chili powder, cumin, oregano, black pepper, and salt. Saute for 2 minutes more. Add to bowl of slow cooker.
To ingredients in slow cooker, add tomato paste, brown sugar, water / stock, diced tomatoes, crushed tomatoes, beans, and bay leaves. Stir everything to combine.
Cook on low for 7 to 9 hours or high for 4 to 5 hours. (After cooking, the slow cooker can switch to “warm” until you are ready to serve the chili.)
Taste and season with some salt and black pepper, if needed.
Serve chili with your favorite toppings.