Currently there are 1 native Telephoto Zoom 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 and none of these lenses have optical Image Stabilization.
Since Fujifilm GFX 50S has environmental sealings (Weather Sealing), you may like to couple your camera with one of these 1 Telephoto Zoom lenses with Weather Sealings.