Congratulations on your good luck! And the answer is “No” your Lopi does not need a stovepipe damper.
Here’s the good news. Creosote build-up is much, much less using an EPA-rated modern wood-burning stove compared to the stoves sold prior to the EPA regulations. EPA has required stove manufacturers to reduce air emissions. Emission reductions are commonly done in one of two ways: (1) catalysts or (2) secondary combustion. Lopi uses secondary combustion.
In older stoves, much of the volatile gases and hydrocarbons produced when burning wood would go up the chimney. These gases often would condense in the chimney to produce creosote. With modern EPA-rated stoves, these gases are burned up before leaving the firebox. In other words, with newer stoves, wood burns cleaner and more efficiently. The result is more BTUs of heat for your home, cleaner air, and less creosote build up.
I had an old non-EPA Fisher stove. My stove pipe had a damper. I’d clean the chimney ever two cords of wood burned. With my Lopi, I have never cleaned the chimney. It’s in the guest cabin, so it isn’t used too much. But I’ve put about six cords through it since I bought it several years ago and the chimney still doesn’t need cleaning.