dll files or interacts directly through their own D3D or DXGI. It gets a bit complicated if you have multiple API’s working like this where there’s Steam files even without Steam or GOG Galaxy in the Steam version without GOG running and then possible issues around if Galaxy has it’s stand-alone Galaxy 32 or 64-bit. My own preference is to use the SpecialK stuff locally though as D3D11.dll or DXGI.dll and on that note check so that GOG Galaxy doesn’t have their own D3D11 or DXGI dll files already present if that’s a potential conflict as well.
I’d try with GOG Galaxy disabled also but I think it should work depending on how it hooks into the API. To the SpecialK config file to disable the Steam functionality, sometimes GOG Galaxy and Steam API files kinda both exists in either version of the game and that can be problematic for compatibility. Hmm if there’s a Steam_Api64.dll file in where Witcher3.exe resides I wonder if you might not have to add
