Heat the oil in a large Dutch oven over medium heat. Add the ground beef and cook, breaking it into crumbles, until browned. Drain excess fat if necessary.
Add the onion, red and green bell peppers, and grated carrots. Cook for 10–12 minutes, stirring occasionally, until the vegetables have softened.
Add the garlic and tomato paste and cook for about 1 minute, stirring frequently.
Add the chili powder, cumin, smoked paprika, oregano, chipotle chile powder, salt and black pepper. Cook for about 30 seconds, stirring, until fragrant.
Stir in the lentils and 1½ cups broth. Bring to a low boil, then reduce the heat to maintain a gentle simmer. Partially cover and cook for 35–40 minutes, stirring occasionally, until the lentils are beginning to become tender. Add up to ½ cup additional broth, as needed, if the chili becomes too thick or you prefer a looser consistency.
Stir in the diced tomatoes with their juices and both kidney beans.
Simmer uncovered for another 35–40 minutes, stirring occasionally, until the lentils are fully tender and the chili has thickened.
Taste and adjust the seasoning if needed. Serve with Greek yogurt, diced avocado, shredded sharp cheddar, fresh cilantro or other favorite toppings.