Sear and Season the Protein: Heat the olive oil in a large skillet over medium-high heat. Add the ground turkey or beef, breaking it apart with a wooden spoon. Sprinkle 2 tablespoons of the taco seasoning over the meat. Cook until the meat is browned and no longer pink (about 8–10 minutes). This ensures a savory crust and prevents a "boiled" meat texture.
Load the Slow Cooker: Transfer the browned meat into a 5-quart (or larger) slow cooker. Add the cubed sweet potatoes, diced onion, bell pepper, minced jalapeño, black beans, and corn.
Build the Broth: Pour in the drained diced tomatoes, tomato sauce, and chicken broth. Sprinkle in the remaining 2 tablespoons of taco seasoning, the cumin, chili powder, and salt. Stir everything thoroughly until the ingredients are well-distributed.
Slow Simmer: Cover the slow cooker with the lid. Cook on Low for 7 hours or on High for 4 hours. The sweet potatoes should be fork-tender and the kitchen should smell incredible.
The Quinoa Finish: About one hour before serving (if on Low) or 30 minutes before (if on High), stir in the uncooked quinoa. Re-cover and let it finish cooking. The quinoa will soak up the excess liquid, swelling into tender, translucent pearls.
Garnish and Serve: Give the chili one final stir. Taste and adjust salt if necessary. Ladle into deep bowls and top with your favorite fixings—shredded cheddar, a dollop of sour cream, and fresh green onions.