There isn’t really a standard lens for it, it’s whatever you want to shoot (mainly handheld). The bellows will focus a 150mm to infinity, and it can go down to a 47mm with a flat plate mount, without bellows. The whole front plate is secured with a clip at one edge and magnets at the other so can switched easily.
For most lenses you would just unscrew the four thumbscrews on the front, then unscrew the 4 steel spacer bars beneath them and swap them for longer/shorter ones depending on your lens.
The lens on the camera is mine, it won’t come with one as standard but uses any large format lens/shutter with a rear element smaller than 65mm diameter (to fit through the helicoid)