It would appear that there is still the possibility that Affinity Photo can have issues with the color/gamut when developing certain RAW files. I know this was a big issue addressed in the v1.5 update as referenced here, but it would appear that there is still work that could be done to improve this behavior.
In all of the test photos, only Fuji RAW File Converter 3.x (SilkyPix 8.x engine) correctly rendered the color of the subject (ring) and didn't clip the colors. RawTherapee, DarkTable, LightZone, and CaptureOne v11 (Fuji) rendered it cool blue. All images are rendered with all processing off/neutral/default to ensure consistency.
For the Affinity Photo HDR and Median Stack images, I used a DCRAW script to dump both subframes from the RAF and composited them accordingly. As you can see, the development result is far superior to what the Serif RAW engine can produce.
Affinity Photo (RAW Develop):
Affinity Photo (HDR Merge):
Affinity Photo (Median Stack):