Heat the oil in a large, deep skillet or Dutch oven over medium-high heat. Brown the ground beef, breaking the meat up as it cooks. Season with a pinch of salt and pepper. Cook until mostly cooked through, about 5-6 minutes. Drain excess fat, leaving about 1 tablespoon in the pan.
Reduce heat to medium. Add the onion, bell pepper, optional jalapeno, and celery. Cook, stirring occasionally, until softened, about 5 minutes.
Add garlic and andouille sausage. Cook another 60 seconds until fragrant and the andouille browns.
Push the meat and vegetable mixture to the sides of the pan. Add the butter to the center and let it melt. Sprinkle in the flour and stir constantly for about 1-2 minutes to cook off the raw flour taste. This is your roux, the step that makes it taste like dirty rice and thickens the final sauce.
Stir in tomato paste, Worcestershire sauce, and Lipton Beefy Onion Soup Mix packet. Pour in 2 cups beef broth gradually, stirring to incorporate the roux.
Add Cajun seasoning, smoked paprika, and black pepper. Bring to a simmer and cook 10 minutes, stirring occasionally, until the sauce thickens and darkens. Taste and adjust salt.
While the sauce is cooking, bring a large pot of salted water to a boil. Cook the spaghetti noodles until al dente according to package directions. Reserve 1/2 cup pasta water, then drain and set aside.
Add the drained spaghetti to the pan sauce and toss to coat. Add a splash of reserved pasta water if needed to loosen the sauce. Everything should be dark, clingy, and saucy, not soupy.
Serve onto plates and top with freshly chopped green onion and parsley, and red pepper flakes to taste. Serve immediately.