Heat the oil in a large pot over medium flame. Add the onion and garlic. Cook for about 3-5 minutes, until fragrant. Add the chipotle pepper and adobo sauce in the last minute of cooking and stir to incorporate.
To the same pot, add the beans, tomatoes with juices, corn, yellow pepper, spices, and broth. Stir well and add chicken breasts (push them down to submerge). Bring the soup to a boil, cover it, and turn the heat down to simmer. Let the soup cook for 25-30 minutes.
Remove the chicken and cut into the middle to check for doneness. If juices run clear, shred with two forks or by hand. Taste the soup and adjust spices as needed. Add the chicken back in and stir.
Divide into meal prep containers and top with cheese and green onion if using. Add avocado and tortilla chips right before eating if desired.