Soak the dried beans overnight in water. Drain and rinse the beans before using them.
In a slow cooker, add the soaked beans, chopped onion, minced garlic, and bacon (if using).
Pour in the maple syrup, apple cider vinegar, ground mustard, black pepper, and salt.
Add the vegetable broth or water to cover the beans. Stir everything to combine.
Set the slow cooker on low and cook for 6-8 hours, or until the beans are tender and the flavors have melded together.
Stir halfway through the cooking time for even cooking.
Taste and adjust the seasoning, adding more maple syrup, salt, or pepper if needed.
Once the beans are tender, remove from the slow cooker and serve immediately.