Don't want to bring this too much OT but let me just say this:
Galaxy needs a few tiny additional files so that it can handle a game on GOG. In the past they simply upgraded the installers so that they contain these files as well. People complained that they have Galaxy related stuff in their offline installers so maybe they followed those copmplaints and decided to not include those Galaxy files anymore in offline installers (it's getting more likely since today I was told the same happened with the just released Deus Ex game). Without those files Galaxy simply does NOTHING when pressing "Play". No error - no nothing. So if you'd like to use 100% identical files without having included those files already (again, they had them included before) and still make the game launching in Galaxy, Galaxy would need to check for these missing files on each launch and Galaxy users probably would not like this. I agree with you that those files don't harm so put them in every installer ... but like I said - there was a thread with complaints about the fact that "Galaxy files" are still in the offline installers which are supposed to be Gaalxy free.

Yes, I tried and yes it did which was expected since Galaxy simply redownloads those missing files whenever you verify the game files. Since this happened now for two different games (and also two different users) I guess it is intended behavior but I still might be wrong here.

Thanks for the update, i had deliberate on getting a refund too, glad i held off.

New candidate:
https://www.gog.com/forum/deus_ex_mankind_divided/game_is_missing_the_outfitweapon_dlcs/post40
https://www.gog.com/forum/deus_ex_mankind_divided/game_is_missing_the_outfitweapon_dlcs

Sigh...

That was quick. Added to OP.

I'm not sure if you tested yourself but the latest version still crashes at start-up for me if I block the exe from connecting out with a firewall. I have many installer versions (going back years) of For The King and all I've tried have this b.s. requirement.

I didn't check that, but I did test that the game was playable with no network (ethernet and wifi disconnected). I had no problem playing the game under these conditions.

And it seems another DLC does not work without galaxy:
https://www.gog.com/forum/dungeon_siege_series/dlc_dungeon_siege_iii_doesnt_work/post12
https://www.gog.com/forum/dungeon_siege_series/dlc_dungeon_siege_iii_doesnt_work

Reported as resolved: https://www.gog.com/forum/general/the_what_did_just_update_thread/post23814

Reported as resolved: https://www.gog.com/forum/deus_ex_mankind_divided/game_is_missing_the_outfitweapon_dlcs/post141

Thank god this list only contains 1 item now.
But I've just updated the D:OS installer.. doh.
Luckily there's that mod..

I'm unable to launch Railway Empire and Dungeons 3 outside of galaxy. They crash before main menu. They both work perfectly fine when launching from Galaxy.

Can Divinity: Original Sin be removed from this list now? I've just installed Divinity: Original Sin Enhanced Edition using GOG Galaxy, and afterwards the Game.pak file was exactly the same as the one in the mod that everybody refers to (an exact binary match). So it seems that GOG have fixed the issue, and that the Game.pak file that now gets installed by default is the working one?

While I agree to a certain extends if the game uses matchmaking or international ranking lists, luckily this thread is not about DRM anyway, but about the use of Galaxy.

I do not use galaxy.

What I did --- just now --- is download the offline installer from GOG's website, install the game, load a game save and check whether the bug still exists. It does.

Which shouldn't be too surprising as the installer files are bit-by-bit identical to the ones I last downloaded in October 2020.

So, perhaps GOG fixed it on galaxy, but they didn't fix it in the offline installer.

P.S. Sorry for the late reply. I have been abroad and have returned only yesterday.