Heat the olive oil in a medium Dutch oven or soup pot over medium heat. When the oil is hot and shimmering, add the carrots, celery ribs, onion, garlic, and a pinch of kosher salt. Cook for about 6 minutes, or until the vegetables are beginning to soften.
Add the sweet potato, bone broth (6 cups for a thicker soup, 7 cups for a brothier soup), ginger, and cayenne (if using), and bring to a simmer.
When the soup is simmering, slice the chicken breasts in half crosswise (this will help them cook more quickly!), and add them to the pot. Simmer for 20 minutes or until the chicken is cooked through and the sweet potato is tender.
Transfer the chicken to a cutting board. and shred using two forks. Fish the pieces of ginger from the soup and discard.
Return the shredded chicken to the pot. Stir in the lemon juice. Taste the soup and season with extra salt and pepper if needed.
Ladle the soup into bowls and garnish with cilantro and avocado or toppings of your choice!