I have a lot of GoG games, and only one so far that won't run on my PC. I have had a couple of problems with their Linux/Wine setups.
If a game doesn't work for you, and support can't get it working, GoG will give you a refund.
You should be able to download via your browser, if you don't want to use Galaxy. Just log into your account, and go to your Library. You should get a display of your games, and selecting one brings you to a screen with download options. (Linux users have to do it this way.)
Yeah. Buy a goddam book. It's a bookstore, ain't it? Don't just go peeking at them! Buy one! I'm Bugak gro-Bol, and I say you better buy a goddam book. And right away, dammit!