https://www.gog.com/en/news/bmore_ways_to_play_your_gog_games_were_teaming_up_with_luna_cloud_streaming_serviceb
More ways to play your GOG games – we’re teaming up with Luna cloud streaming service!
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)