If your soup is to be dairy free as well as gluten free, choose a dairy alternative with a neutral flavor. While coconut milk would add a thick, creamy texture, the coconut flavor will be more noticeable in the soup. Instead, select almond milk or cashew milk or my cashew coconut milk which has limited coconut so no flavor changing issues. I don't recommend oat milk in dishes that will be cooked as the oatmeal used to make it actually begins to cook and create a cereal/porridge texture.