In a large Dutch oven, or large heavy bottom sauce pan, heat oil over medium high heat. Add andouille sausage, and brown on both sides for about 2 - 3 minutes. Remove sausage and let rest on plate.
To make the roux, reduce heat to medium-low. Add the bacon or duck fat and whisk in flour. Continuously whisk until roux is a dark brown color. This process can take between 20 - 25 minutes or longer, depending on heat level. It is important to consistently whisk to prevent roux from burning.
Stir bell pepper, onions and celery into roux mixture. Cook, stirring constantly for about 5 minutes. Stir in diced tomatoes, and continue to cook for about 3 minutes, constantly stirring. Stir in sausage and garlic.
Add beef broth and water. Stir or whisk together until the liquid is thoroughly mixed with the roux, and there are no visible lumps. Add thyme sprigs, old bay, oregano, hot sauce, sugar, cayenne pepper, oyster sauce and bay leaves. Stir together, or whisk until everything is blended completely. Bring to a simmer, then reduce heat to low. Simmer covered for 1 hour, stirring occasionally.
After gumbo has simmered for 1 hour, heat a small skillet over medium heat. Add the frozen okra and apple cider vinegar. Cook for about 8 minutes, then use a slotted spoon to add the okra to the gumbo. Continue to simmer for 1 hour, stirring occasionally.
Stir in shrimp and crab meat. Cook for 5 additional minutes until shrimp is pink in color. Taste and add salt if needed.
Remove bay leaves and thyme sprigs. Serve hot with cooked rice.