It is kind of hard to support Galaxy before it is available. When Larian first confirmed Galaxy support they said the end of August; I have not been following GOG news to see if it is still on track.
Larian has confirmed there will be a Linux release, they just have not announced an ETA. After the PC and Mac releases is that terribly surprising? In response to a tweet asking if it would be released this year, Larian responded "We certainly hope so!", which, unless you are a pessimist, implies a release well before the end of the year.