Here is a crazy idea. Maybe virusscan sees a false positive but is unable to do so when the game gets launched via Galaxy?

I dunno if this is applicable, but have you turned Galaxy's overlay off?

I never use the overlay. It's always turned off on my end.

2023 is almost over but this problem still exists.

It's 100% a problem caused by GOG Galaxy as the same thing also happened with Turok 2 today. I did a fresh installation of the game, started it using the Desktop shortcut and nothing happened. Then I tried to start it using the game exe in the install folder and also nothing happened. Then I realized that I had GOG Galaxy still open because I used it to download the offline installer files. I closed GOG Galaxy and started the game again using the Desktop shortcut and tada the game launched just fine.

I really want to know now why GOG Galaxy prevents some games from launching while others just work 100% fine no matter which way you start them.

Ruiner, the first free game (Followed by loop hero) i got on EGS a couple years ago when they started trying to go head to head with Valve/steam...

If i remember right, it was kinda a hyper violence game similar vein to to Hotline Miami.

Most games don't directly launch their executables, but instead conga though a startup script. Try the executable directly.

I tried that already as you can see in the videos I posted in an previous post. Galaxy just blocks the executable from launching as long as it's opened.

Are we sure that's the actual game executable?

Either way, sounds like a good reason to open a terminal and launch the thing to see what hell GOG Galaxy has wrougt and check for logs.

100% it is. I forwarded this stuff to the GOG support now. I hope they know how to fix this.

I tried that, Turok 2 works without problems with or without Galaxy. They can't fix what's not broken.

There is something terribly wrong with your system and it's not Galaxy. Because then it would not work on any computer that has Galaxy installed. It's just yours.

If support can't give you tips how to solve the problem, then you should think about a clean install of your OS. How about a clean install or try another computer?

If you want to be sure that Galaxy is not used at all, delete the according DLLs from the game. If it hasn't any Galaxy DLLs, all the better. Then the launcher does not communicate with the game at all and just launches it's .exe.

I can confirm the Ruiner thing. If I install through Galaxy, the game only launches through Galaxy. Trying through the .exes, nothing happens (both Ruiner.exe or Ruiner-Win64-Shipping.exe). Doesn't matter if Galaxy is running or not.

Deleting the Galaxy files in Engine/Binaries/ThirdParty/GOG/Win64/, the game can be launched normally from the .exe. When I restored that from Recycle Bin, the game can no longer be launched through the .exe.

Can confirm deleating the DLL files make the game launch fine through the game EXE with Galaxy still running. It would be really interesting to hear what GOG has to say about Galaxy DLL files acting as some kind of DRM on some games.

For Turok 2 it's also the Galaxy64.dll causing the problem.

When I replaced that DLL with a different one (tested it with the Quake 2 Enhanced Galaxy64.dll) the game was starting fine via game EXE even with Galaxy running in the background. The DLL that comes with the latest Turok 2 offline installer of via GOG Galaxy installation is simply broken in some way. GOG needs to update the installer/installation files.

I installed using the OL installers (which usually does not make a difference) and was able to run Ruiner fromthe launch shortcut with and without Galaxy running.

I can't give you an educated answer as I have never installed Galaxy and never will if there's an alternative, but it sounds to me that Galaxy is using some kind of file lock on those files which prevents using them.

Is it possible that Galaxy somehow thinks the download is not yet completed, and keeps the file locked as an active download?

Something like that has happened to me with other software.
Sometimes it has even happened with game downloads that the download is actually complete, but the browser doesn't realise that, and doesn't rename the complete file automatically. It's obviously a completely different problem than yours, but my guess would be that Galaxy thinks the download is still active and needs to be completed.

Joining club, lost 260 legendary achievements and several games didn't catch up at all. I will buy and install RUINER without Galaxy... And make it work... All games must work without a client...
edit:
Game bought...
... downloading offline installers (up to 6,5MB/s)
... disconnecting from the internet and installing a game to launch right after...game installed on Windows 10_64bit... won`t start...asking for DirectX_Runtime...
...downloading https://www.microsoft.com/en-gb/download/details.aspx?id=35 and installing...
...game works fine offline... plot fits the thread lol...
It works from offline installers downloaded through a web browser.