Hello,
I saw on the game page that it will work on Windows. However, on its Steam page, there is also support for Linux.

I would like to ask, will GOG version of the DLC work also on Linux?

Hi,
if there'll be Linux/Mac support, GOG will probably try to add these. Though, only Windows is a certainty for now.

I hope they do, i already bought it without thinking that there might not be Linux support.