Season the chicken with salt, pepper, and a pinch of taco seasoning. In a large pot or Dutch oven, heat the oil over medium heat. Sear the chicken for 5-6 minutes per side until golden but not fully cooked. Remove and set aside.
In the same pot, add the diced onion, garlic, bell pepper, and jalapeño (if using). Sauté for 3-4 minutes until softened.
Stir in the black beans, pinto beans, corn, diced tomatoes, green chiles, chicken broth, taco seasoning, cumin, chili powder, and smoked paprika. Mix well.
Return the chicken to the pot. Bring the soup to a boil, then reduce the heat to low and let it simmer for 20-25 minutes, or until the chicken is fully cooked and tender.
Remove the chicken from the pot and shred it using two forks. Return the shredded chicken to the soup.
Stir in the lime juice and fresh cilantro. Taste and adjust seasoning with salt and pepper if needed.
Ladle the soup into bowls and top with your favourite toppings: shredded cheese, sour cream, avocado slices, crushed tortilla chips, or a dollop of guacamole.