Hi, I'm somewhat confused about your post. Is the files readout by rrgn not encrypted.
I own a Instinct Solar watch, unlike Instinct without solar, a entropy test revealed the GCD firmware file is encrypted, but I would be interested if I can manage to dump the unencrypted content from the watch using rrgn. And (hopefully) I can then find out how the GCD firmware is encrypted. My watch is too compact to have a SD card slot, and there is only 4.5MB space left, so I'm not sure whether I can do the same rrgn dump. Could you please share the rrgn dumped file and I can try my luck with GHIDRA, it's possible that the way garmin encrypts the firmware is the similar with different devices.