Yes, you can convert a carport to a sunroom. Carports are designed to support the full weight of a car for extended periods of time so they should be able to hold the extra weight from the glass walls and roof.
Growing up the first sunroom I ever saw was our neighbors who converted their carport to a garage. This quickly became a favorite hangout for their teenage sons and me. We had a TV and super Nintendo setup in the room, and I spent so many hours after school in their sun room.
As an after school hangout, it was perfect as we would just hang out there, and there was no need to tromp through the whole home. It was a nice way of separating us teenagers who I’m sure were loud away from the adults in the rest of the home.