Drain and rinse the canned black beans. Set them aside while you prepare the vegetables.
Dice the onion, bell pepper, carrots, and celery. Mince the garlic and finely chop the jalapeño, if using.
Add the black beans, onion, bell pepper, carrots, celery, garlic, jalapeño, diced tomatoes, vegetable broth, and tomato paste to the slow cooker.
Add the ground cumin, chili powder, smoked paprika, dried oregano, salt, black pepper, and olive oil, if using.
Stir the ingredients gently until the beans, vegetables, broth, and seasonings are well combined.
Cover the slow cooker and cook on LOW for 4–6 hours or HIGH for 2–3 hours, until the vegetables are tender and the flavors have blended.
For a thicker soup, use an immersion blender to partially blend the soup directly in the slow cooker. Leave some beans and vegetables whole for texture.
Alternatively, transfer 1–2 cups of the soup to a blender, blend carefully, and return it to the slow cooker.
Stir in the fresh lime juice after cooking.
Taste the soup and adjust the salt, pepper, chili powder, or lime juice as needed.
Stir in some of the chopped cilantro or reserve it for garnish.
Ladle the soup into bowls and top with fresh cilantro, avocado, lime wedges, diced onion, tortilla strips, sour cream, cheese, or hot sauce.
Serve hot with warm tortillas, cornbread, rice, tortilla chips, or a simple green salad.