Place the broth, potatoes, onion, and garlic into the slow cooker or instant pot.
For the Slow cooker, cook on high for 3-4 hours or until the potatoes are tender.For the Instant Pot, cook on the soup setting for 3 minutes.
When finished, using an immersion blender, blend the soup thoroughly. Mix in the salt and nutritional yeast. If the soup is thicker than you like, add more broth until the desired consistency is reached.