Soak the cashews in boiling water for 20 minutes, then drain and set aside.
Cook the chopped bacon in a large pot over medium heat until crisp, about 8 minutes. Lift it out onto a paper towel and pour off all but 2 tablespoons of the fat.
Cook the onion in the reserved fat for 5 minutes until soft, then add the garlic and cook 1 minute longer.
Add the cubed potatoes and chicken broth, bring to a boil, then simmer for 18 to 20 minutes until the potatoes fall apart when pressed.
Transfer 2 cups of the potatoes with a little broth to a blender along with the drained cashews, oat milk, and nutritional yeast. Blend for 90 seconds until completely silky, then stir it back into the pot.
Mash the remaining potatoes lightly right in the pot so the soup keeps some rustic texture. Stir in the dairy free butter, salt, pepper, and smoked paprika and warm through.
Finish with the lemon juice, then ladle into bowls and top with the crisp bacon, dairy free cheddar shreds, and green onions.