This medium format camera would set you back something over US$7500 for body and a lens. Unlike Fuji X APS-C cameras, the sensor uses a Bayer color filter array. However, Fuji kept the .RAF file extension name (the page at the link incorrectly refers to .CR2).
RawTherapee dev now supports the new compressed bayer raw format from Fujifilm, used by the Fujifilm GFX 50S medium format camera. This feature will be part of RawTherapee 5.1.