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)

If only that were a long term solution. Heroic works for me on average for a week and then fails to connect to game stores and even forgets where the games are installed sometimes.

It fails on my laptop and my steamdeck. I love when it works but it's not consistent.

You can do that, but some of the features only work if you launch the game through Galaxy. Cloud saves only work that way. Some games need it for online matchmaking or leaderboards. It handles updates. If you care about achievements or statistics you won't get any of those without Galaxy.

Just downloading the game from the website is usually good enough for actual old games, but it's just a second class experience for most newer games. That bothers some people more than others. I'm mostly just annoyed by the principle of the thing, really.