In an interview with PC Gamer, Kiciński and managing director Maciej Gołębiewski were asked whether GOG had plans to focus more on Linux going forward, given a growth in pro-Linux and anti-Windows sentiment among some PC players.
“Yes, we are,” Gołębiewski replied, stating that Linux was “one of the things that we’ve put in our strategy for this year to look closer at”.
“I don’t want to commit to any specifics, but certainly you will see this trend, and we also see that Linux is close to the hearts of our users, so we probably could do better on that front, and that’s something that we’ll be looking at,” he added.
Kiciński then addressed the current state of Windows, saying he was “really surprised” that it continues to hold such a large market share despite its issues.
“It’s such poor-quality software and product, and I’m so surprised that it’s [spent] so many years on the market,” he said. “I can’t believe it.”
(GOG founded 22 February 2008)
You can select versions using Heroic Games Launcher as well. It's a little bit hidden as you need to select "Modify installation", but it's there. As far as I know it's not a limitation by HGL that it can only select 5 versions, that's just how many versions GOG have made available.