unfortunately, as of yet, I have not been able to get the GoG version installed via Heroic to work. If you browse for alternative EXE there is an x64 and x64_dx12 folder, choosing witcher3 from the former says it's running, the program uses lots of CPU... but the game never starts. I could try using galaxy directly, but this requires a redownload :S I'll do it #ForScience and let you know what I found