Heat a large skillet over medium heat. Add the ground beef and cook, breaking it up, until mostly browned, about 4 to 5 minutes. Stir in the diced onion and cook until softened, about 3 minutes. Add the minced garlic and cook 30 seconds more until fragrant. Drain off excess fat if needed.

Add the potatoes, carrots, celery, kidney beans, diced tomatoes, tomato sauce, beef broth, Worcestershire sauce, paprika, thyme, bay leaf, salt, and pepper to the slow cooker. Spoon the browned beef and onion mixture over the top and gently stir to combine. Add the optional sugar if your tomatoes tasted sharp.

Cover and cook on LOW for 7 to 8 hours (preferred) or HIGH for 3 to 4 hours, until the potatoes and carrots are fork-tender and the broth has thickened slightly. Avoid lifting the lid during cooking.

Remove and discard the bay leaf. Taste and adjust seasoning as needed. Add salt, pepper, or a splash of apple cider vinegar to brighten the flavor. Ladle into bowls and serve hot.