Currently there are 3 native Telephoto Prime lenses for Fujifilm GFX 50S and all of these lenses are autofocus (AF) type.
Fujifilm GFX 50S doesn't have a sensor based image stabilization system but 1 of these Telephoto Prime lenses features optical image stabilization.
Since Fujifilm GFX 50S has environmental sealings (Weather Sealing), you may like to couple your camera with one of these 3 Telephoto Prime lenses with Weather Sealings.