Add potatoes, onion, garlic, bell pepper, celery, smoked paprika, Cajun seasoning, thyme, salt, pepper, and broth to the slow cooker.
Cover and cook on low for 6–7 hours or high for 3–4 hours, until potatoes are tender.
Use a potato masher or immersion blender to mash some of the potatoes, leaving some chunks for texture.
Stir in cream, butter, and cayenne pepper if using.
Cook on high for another 15–20 minutes until heated through.
Taste and adjust seasoning as needed.
Serve hot, garnished with cheddar cheese and green onions. Enjoy this slow cooker Cajun potato soup warm and comforting.