Originally Posted by ForkTong
Should work now. Will only work on Steam keys that were created before the release of the game, i.e. Alpha and Beta keys.

I activated the Steam key for the Early Access, but had chosen GOG for my final copy. I've been checking my Larian Vault KS backer page every day, and I still have the red banner telling me to check back later if I want to change my Steam key into a GOG key.