Add 1 pound smoked sausage to a large pot. Stir and cook over medium heat until browned, about 4 minutes.
Add 1 cup diced onion and cook for 3 minutes before adding 1 tablespoon minced garlic and cooking for an additional minute.
Add 1 pound Yukon gold potatoes and 4 cups chicken broth.
Bring the soup to a simmer over medium heat, then reduce the heat to medium-low and stir in 2 (15-ounce) cans turnip greens, 2 (14-ounce) cans drained and rinsed Navy beans, 1 (14.5-ounce) can tomatoes and diced chiles, and ½ teaspoon Cajun seasoning.
Season with salt and ground black pepper to taste. Simmer for 25-30 minutes before serving.
