Potatoes can be used to thicken soup and the addition of the potatoes will also make the soup much better.
I've added mashed potatoes to some soup to make the soup thicker and it worked just fine.
You can also add some flour or cornstarch to the soup which also thickens it.
Another way to thicken soup and give it a good flavor is to add either some full fat milk to the soup or add some sour cream.
Add the milk or sour cream a little at a time and stir it in the soup until the soup becomes the thickness you want.
I like sour cream and milk added to my soups and it gives the soup a rich creamy taste.
I always add sour cream and milk to most of my soups and I love it that way.