
Heat oil in a large heavy pot over medium-high heat. Add turkey; cook, stirring often to crumble, until browned, about 5 minutes. Add onion and garlic; cook, stirring often, until softened, about 5 minutes. Add chipotle; cook, stirring constantly, until fragrant, about 1 minute. Stir in tomatoes, sweet potatoes, broth and salt. Bring to a simmer over medium-high heat. Cover; reduce heat to medium and simmer until the sweet potatoes are tender, about 20 minutes.
Uncover the pot; continue simmering over medium heat, stirring occasionally, until the chili slightly thickens, about 10 minutes, or until desired consistency. Stir in lime juice.
Divide the chili evenly among 6 bowls; garnish with avocado, if desired.