Dice the bacon and cook it in a large skillet over medium heat until browned and mostly crisp. Transfer the bacon to a paper-towel-lined plate, leaving about 1–2 tablespoons of bacon fat in the skillet.

Add the lean ground beef and chopped yellow onion to the same skillet. Cook until the beef is browned and the onion is tender, breaking the beef into small crumbles, then drain the excess grease.

Add the undrained pork and beans, drained and rinsed kidney beans, drained and rinsed butter or lima beans, cooked bacon, browned beef, and onion to a 5- to 6-quart slow cooker.

Stir in the ketchup, barbecue sauce, packed light brown sugar, molasses, yellow mustard, Worcestershire sauce, and black pepper until the sauce is evenly distributed.

Cover and cook on LOW for 4–6 hours or HIGH for 2–3 hours. Stir once or twice if convenient, and cook until the beans are hot, thick, and glossy.

Taste the finished beans before adding salt because the bacon and canned beans may already provide enough seasoning. If the sauce needs more thickness, let the beans stand uncovered for 10–15 minutes; if they become too thick, stir in a few tablespoons of water or additional barbecue sauce.