Heat a large pot over medium-high heat. Break sausage into chunks and put in the pot; cook and stir until completely browned, 5 to 7 minutes.
Transfer cooked sausage to a slow cooker. Add water, chicken broth, tomatoes, lentils, onion, celery, carrot, and garlic. Season mixture with garlic powder, parsley, oregano, pepper, basil, rosemary, and salt.
Cook on Low until lentils are tender, about 4 hours.
Stir cabbage into the soup; continue cooking until the cabbage is softened, 15 to 20 minutes.
