Preheat the smoker to 250°F. Set out a rimmed baking sheet or a small smoker-safe tray for the meatloaf.
In a large bowl, combine the ground beef, diced Andouille sausage, egg, almond flour, onion, 1 tablespoon Dijon mustard, Worcestershire sauce, Cajun seasoning, garlic powder, smoked paprika, salt, and black pepper. Mix gently with your hands just until everything is evenly combined. Avoid packing the mixture tightly.
Shape the mixture into a compact loaf on the tray, smoothing the sides so it cooks evenly. Place it in the smoker and cook until the center reaches 160°F when checked with an instant-read thermometer, about 2 to 2½ hours depending on the loaf’s shape and the smoker.
While the meatloaf smokes, make the slaw. In a medium bowl, stir together the mayonnaise, apple cider vinegar, the remaining 1 teaspoon Dijon mustard, and celery seed. Add the green and red cabbage and toss until coated. Cover and refrigerate until ready to serve.
Remove the meatloaf from the smoker and let it rest for 10 minutes before slicing. Serve with the chilled creamy slaw on the side.