Same issue (iOS, iPhone X). I've seen several other posts about this as well.
Does the flash not function in raw/DNG mode? If so, just tell us Adobe. Is this a bug or expected behavior?
On my iPhone 7 it worked just fine. Also, when I want to take a selfie in DNG-modus (not sure if that's what you want by the way..) I was able to enable the 'flash' (so the screen becomes bright). It seems that it's a bug in the connection between the app and the flashlight.
I have the same problem here. I believe it an issue with the iOS. I tried using the Camera+ app as well and when I changed the image quality to RAW I got this message:
"RAW and Flash Warning :: RAW shooting is currently not compatible with flash on this device. Until a fix is available in a future iOS version, flash will be automatically turned off for you when you are capturing RAW photos. Please, disable RAW manually if you need flash"
Very frustrating, and stupid.