According to
this thread they are currently only planning on having a Steam and PS4 release, but might bring it to "other platforms" in the future.
The reason given though is that as a small team bringing the game to multiple platforms is too much effort. This sounds disingenuous to me, since sending GOG their PC build should take far less effort than building a console port and I've seen way smaller teams than theirs release games simultaneously. Can anyone here explain how much effort it actually takes to maintain a GOG version next to a Steam version?