For the Chili: Heat the oil in a large saucepan or pot over medium heat. Add the onion and bell pepper, sprinkle with salt and pepper and sautéed until the onion begins to brown, about 5 minutes. Add the sausages and sauté until beginning to brown, about 5 minutes. Add the cumin, coriander, chili powder, and red pepper flakes. Cook until the spices are fragrant, about 1 minute. Mix in both cans of beans with their liquid, tomatoes, and 1½ cups water.
Bring the chili to a boil. Reduce the heat so the mixture simmers, and cook until it thickens and flavors blend, stirring occasionally, about 20 minutes. Thin with additional water if the chili is too thick. Season to taste with salt and pepper.
Meanwhile, prepare the Topping: Combine the yogurt, lime juice, and lime zest in a small bowl and mix to blend. Season to taste with salt and pepper.
Spoon the chili into bowls. Top each with a dollop of the yogurt topping and serve.