Hi Chris
Unfortunately it is not on the list for High Sierra. Indeed I cannot open the G9 RAW files in 'Preview' or see them in the Finder. This is where it gets messy! Within Affinity, Serif Labs or Apple Core WILL open a G9 RW2 file, but not if it uses the High Resolution mode. Even more messy, a normal RW2 file from the G9 is opened in Affinity 1.6 with full chromatic aberration correction, but in 1.7 beta there is no correction. I guess this MAY just be a work in progress.
pretty much all my other Apps that accept Camera Raw, like Luminar 3, Silkypix 8, Aurora HDR Pro, Photomatix Pro 6, all accept the G9 files (inc HR) so Affinity is behind the curve! I don't have any Adobe CC Apps so I cannot know where they are.
FWIW