Place the rinsed lentils, sweet potato cubes, diced onion, minced garlic, diced bell pepper, drained black beans, crushed tomatoes, and vegetable broth into the slow cooker.
Sprinkle in the chili powder, cumin, smoked paprika, salt, and black pepper.
Stir everything together until the spices are evenly distributed through the liquid and vegetables.
Cover the slow cooker and cook on low for 7 hours or on high for 4 hours, until the lentils are tender and the sweet potatoes are soft.
Give the chili a final stir, taste, and add a pinch more salt if needed before serving.