Since last update, 2.13 I think, it does not work well with gog games, at least was not able to install flatout and pillars of eternity, both from my gog library. Nonetheless I was able to install pillars from the epic store, using heroic. With flatout I spent a week trying to debug installation problem, clear cache, reinstall of heroic, and everything else and then simply used lutris which installed flatout at first try and let me play right away (steam deck)
I played it first when it was a free mod and then bought on steam and put on my backlog list because I really enjoyed what I saw back then.
Now, wouldn’t be amazing if someone develop, you know, HL3 or at least episode 3? The game script wasn’t published some time ago because of copyright expiration? I would pay for it, and I am sure I am not the only one.