I wanted this and I managed to get it. I hope this saves some poor soul the hours I had to spend trawling through the internet.
I started with an offline installation of No Man’s Sky and I wanted to add the multiplayer, cloud save and automatic updates features provided by GOG Galaxy, without GOG Galaxy showing when I started the game.
First, download the GOG galaxy executable from here. I opened lutris and selected the No Man’s Sky installation (but didn’t start it). To the right of the “start” button, there is a wine icon with an arrow up; if you click it, you get a menu with the option “Run EXE inside Wine prefix”. Use this, then navigate to the downloaded GOG Galaxy exe. Follow install instructions on-screen and make sure to select “launch” after it is done.
In the GOG Galaxy that opens, go to owned games and select NMS. At the top, to the right of the Install button, there is a settings button. In the menu, go to Manage installation → Import folder. Navigate to the install location of NMS (for me C:\GOG Games\No Man’s Sky, I think that’s the default) and it will find the game. It will now also install any updates for the game.
When it’s finished, close Galaxy and return to Lutris. There, right-click the game and select Configure. Go to Game options and change the executable to “[path to your game’s prefix, for examle /home/caedem/GOG Games/NMS]/drive_c/Program Files (x86)/GOG Galaxy/GalaxyClient.exe”. In the Arguments field below, add the following: /command=runGame /gameId=1446213994 /path="C:\GOG Games\No Man's Sky" /launchViaAutostart.
If your path from previously is not C:\GOG Games\No Man’s Sky, don’t forget to change it here too. The gameid used is No Man’s Sky’s gog gameid. The /launchViaAutostart parameter makes GOG Galaxy not show a window, but minimise to tray immediately.
If you have cloud save backup enabled, you will have to wait for that to finish before the game actually starts (this could take a few seconds).
Finally, I guess this would work for any game so long as you use the correct path and gameid. You can find the gameid by going to the game’s installed directory and looking for a file named something along the lines of “goggame-1446213994.hashdb”, with the numbers being the gog game id.
Hope this helps someone!
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