Heat a large skillet over medium heat. Add the ground beef, onion, and garlic. Cook until the beef is browned and the onion softens, breaking up the meat as it cooks.
Transfer the beef mixture to the slow cooker. Add the black beans, diced tomatoes, minced chipotle peppers, chili powder, cumin, smoked paprika, and beef broth.
Stir everything together until the spices are evenly distributed. Season with salt and black pepper.
Cover and cook on low for 6 to 8 hours, until the chili thickens and the flavors meld.
Taste and adjust salt or pepper if needed before serving. Ladle into bowls and top with shredded cheddar cheese and sliced green onions.