Reading an post about CMYK support on Gimp is fascinating. For years, GIMP is my image editor of choice in completion of Krita for web publishing, photography and desktop publishing. The CMYK support debate shows how many designers forgot they mostly work screen in RGB and CMYK is mainly for printing. Because of the different process of ink, there is no guarantee the colours from CMYK will be the same on every printers.
Thankfully, majority of printing computer requires RGB file to avoid headache.