In a large skillet over medium heat, add the ground beef (or turkey). Cook until browned, breaking it up with a wooden spoon, about 5-7 minutes. Drain any excess fat and transfer the meat to the slow cooker.
To the slow cooker, add the kidney beans, black beans, crushed tomatoes, diced onion, minced garlic, diced bell pepper, chili powder, cumin, paprika, salt, black pepper, and broth. Stir to combine all the ingredients well.
Cover the slow cooker and set it to low for 6 hours (or high for 3 hours).
About 30 minutes before serving, taste and adjust seasonings if necessary.
Once cooked, ladle the chili into bowls and garnish with optional toppings if desired.