Preheat oven to 350°F (175°C). In a large Dutch oven or oven-safe pot, cook the diced bacon over medium heat until crispy. Remove bacon with a slotted spoon and set aside, reserving about 2 tablespoons of rendered fat in the pot.

Add the ground beef to the same pot with the reserved bacon fat. Cook over medium-high heat, breaking it up with a spoon, until browned. Drain off any excess grease.

Add the chopped yellow onion to the pot with the browned beef. Cook for 5-7 minutes, until the onion softens. Stir in the minced garlic and cook for another minute until fragrant.

Stir the undrained pork and beans, rinsed and drained cannellini beans, and dark red kidney beans into the pot with the beef mixture.

In a separate bowl, whisk together the ketchup, brown sugar, molasses, apple cider vinegar, Dijon mustard, smoked paprika, salt, black pepper, and cayenne pepper (if using) until well combined.

Pour the sauce mixture over the beans and beef. Stir everything together thoroughly. Stir in half of the crispy bacon (the other half is for topping or garnish).

Bring the bean mixture to a gentle simmer on the stovetop.

Cover the Dutch oven or transfer the mixture to a large oven-safe baking dish and cover with foil. Bake for 60-70 minutes, or until the beans are bubbly and the sauce has thickened to your desired consistency.

Remove from the oven, uncover, and let stand for 5-10 minutes before serving. Garnish with the remaining crispy bacon, if desired.