Pork Tenderloin Gumbo

Name: Pork Tenderloin Gumbo
Ingredients: 1 (1 1/2 pound) pork tenderloin; Kosher salt; Freshly ground black pepper; 1 tablespoon vegetable oil; 12 ounces Andouille sausage or kielbasa, sliced; 3 tablespoons bacon fat or unsalted butter; 1/2 cup all-purpose flour; 1 onion, chopped; 1 green bell pepper, chopped; 3 celery stalks, chopped; 6 cups chicken stock or low sodium chicken broth; 3 cups water; 1 pound fresh or frozen okra; 2 scallions; Cooked white rice for serving