Did you get this resolved? If not, you can install via Galaxy, then go to the game installation folder and create a shortcut to the game's .exe. You should be able to launch from that and can even uninstall Galaxy, I think.
No resolution, and yes I did get it installed via Galaxy that sets up a launch icon on desktop which when clicked on opens Galaxy then the game.
Thanks for the shortcut idea :)
I can confirm that using the shortcuts in the game folder by passes GOG Galaxy. Also, if you download from the the GOG website directly you should have an option to download the classic version which does not include GOG galaxy. However, if you try and download the game using the gog downloader it seems to automatically opt in for the gog galaxy version. Even if you have classic version selected before you choose to use the downloader links.
GOG seems to want to move away from the classic installers. Which makes sense in a way. Less work for them. As long as they dont take away the right to use the game without the client running I am fine with it. I just wish they would make it more clear to people that the default game shortcut often opens gog galaxy with the game. I have seen a fair amount of posts criticizing this and claiming GOG is no longer DRM free and forcing the use of the client. It is not the case. Perhaps GOG should make the default shortcut not open the client. If people want to use the client they can start the client first and start the game from there.
The only advantage to the client is making sure the game is update with out checking at the website, achievements, and more multiplayer functionality. Most of those things I do not utilize so i just play the game with out the client running. Once in a while I will use it for updating but more often I just get the patch directly from the website.
It is nice to have those options though.