In a 4 quart, heavy bottom, oven-safe pot (like a Dutch oven) over medium heat, add ground beef, onion, bell pepper, garlic salt and onion powder. Cook until the ground beef is no longer pink. Drain the excess liquid.
Add cooked bacon crumbles, brown sugar, baked beans, barbecue sauce and dijon mustard. Stir to incorporate all ingredients.
Cover and bake for 1 hour. (When done, the beans should be hot and bubbly and thickened.) Serve warm.
Place potatoes, celery, and carrot in a large pot and cover with water; bring to a boil. Reduce heat to medium-low and simmer until tender, about 20 minutes. Drain and transfer to a 2-quart baking dish.
Melt 3 tablespoons butter in a large skillet over medium heat; cook and stir ham, green bell pepper, and onion until vegetables are tender, about 5 minutes. Transfer ham mixture to baking dish and mix with potatoes, etc.
Melt remaining 1/4 cup butter in a clean skillet; cook and stir flour in melted butter until smooth, about 3 minutes. Gradually stir in milk and season with salt and black pepper. Bring to a boil, stirring constantly, until thickened, about 2 minutes. Add Cheddar cheese; stir until melted. Pour cheese mixture over ham and potatoes. Sprinkle with bread crumbs.
Bake in preheated oven until bubbly, 25 to 30 minutes. Allow casserole to rest for 5 to 10 minutes before serving.