If the smoke has a strong diesel smell, it’s probably unburned fuel. That can be due to low compression, low cylinder temps, and injectors that are not spraying correctly (dirty, sticking, dripping).
My friend just had the cylinder head replaced on his. He tried to tell me his dealer said they are having lots of head/head gasket issues, but I have not heard this.
He also bought it used from a rental place if that tells you anything.
Have you lost any coolant or any pressure in the overflow tank? How is engine and heater temps when operating?