Line a rimmed baking sheet with foil. Spray a wire cooling rack with cooking spray and set on top of the baking sheet.
In a large frying pan, saut the onion, celery, bell pepper, green onion, garlic, and jalapeno(s) in the oil until the vegetables soften, about 5 minutes. Add the beef broth, ketchup, Traeger Cajun Rub, Worcestershire sauce, hot sauce, mustard, and pepper, and stir to combine. Remove from the heat and let cool completely.
In a large mixing bowl, combine the ground beef, pork, and andouille sausage. Add the egg, bread crumbs, and the cooled vegetable mixture. Mix lightly but thoroughly with your hands until well combined.
Form a rectangular loaf about 8 inches long and 1-1/2 to 2 inches high. Lay it on top of the cooling rack.
When ready to cook, start the Traeger grill on Smoke with the lid open until the fire is established (4 to 5 minutes). Put the pan with the meatloaf on the grill grate and smoke for 1 hour. Increase the temperature to 325 and bake the meatloaf for 1 hour.
In the meantime, make the glaze: Combine the ketchup, brown sugar, hot sauce, white vinegar, and mustard in a small saucepan. Simmer for 5 to 10 minutes. Pour the glaze evenly over the meatloaf, or brush it on with a pastry brush. Continue to cook the meatloaf for 30 minutes more, or until the internal temperature in the thickest part is 160F. Let the meatloaf rest for 10 minutes before slicing and serving.