Heat 2 tbsp olive oil in a large pot over medium heat. Add onion and bell pepper; sauté 4–5 minutes until softened.
Add jalapeño (if using) and garlic; cook 30–45 seconds until fragrant.
Stir in cumin, smoked paprika, chili powder and oregano; cook 1 minute to bloom spices. Add diced tomatoes and stir.
Pour in 6 cups chicken broth and bring to a simmer. Add cauliflower rice and simmer 8–10 minutes until tender.
Add shredded chicken and simmer 4–5 minutes to heat through. Stir in 2 tbsp lime juice and adjust salt and pepper.
Serve hot topped with sliced avocado and chopped cilantro. Offer extra lime wedges.