People found a solution and it was posted in another thread.

You can use a patcher (unofficial 3rd party), or an already patched executable or you can use a hex editor and change a byte value in the original Saboteur executable.I can confirm this works.

https://www.gog.com/forum/the_saboteur/game_does_not_start_at_all/post29

https://www.gog.com/forum/the_saboteur/game_does_not_start_at_all/post34

I have contacted GOG support to mention this fix, and they have replied that the appropriate team will look into it.

Been there, done that. As mentioned, it doesn't work.
The game does not launch.

I have, however, managed to launch another copy of the game. One that a friend cracked and installed years agaon on an XP computer I think.
Oddly, this one launches, but my legal GOG version never does.

I just noticed that you want to launch the game on a 4 core PC, so it's normal that the "> 4 core issue" and its fix doesn't affect you. As a matter of fact (albeit maybe not very likely) the fix for the "more than 4 core issue" could have a reverse effect in your case and cause problems since it's not intended for your configuration. I haven't tested that fix for a 4 core CPU PC.

Your problem seems to be different. Does the game not launch at all, or do you get any error message?

Have you contacted support with this? This is not the "more than 4 cores issue" so they will be probably able to help you.

If you have a Hex Editor you could check for differences with the 3rd party exe that works. I wouldn't really recommend running the game with a 3rd party cracked exe, since lots of other stuff can go wrong that way, but at the end of the day, it's what works for you, and how much time you want to spend to make the official executable work the intended way.

Thanks for your reply.

No I haven't yet contacted support because I didn't think I wa the only one running such an issue.
But I'll have too it seems.

What happens is quite simple, I install the game, launch it, from the exe or the gog launcher, then I get a black screen....
And nothing. Bach to before launch.

And not trace of the saboter in the task manager.

I have tried to insert the cracked exe in the gog folder, the cracked exe that launched the game and made it playable on my friend very old installation (working on my actual computer). Replacing the exe given with gog installation.

And then I get stuck in the black screen, this time with an error saying "not enough memory" while I have plenty available, and running 32Gb of RAM....

So, I don't really get it at this point.


EDIT : Filed a report, we'll see.