ssokolow: So far, I've only heard of one game where some kind of post-unpack script had to be run for the Linux version (yay, lack of a Registry), it was contained within the game folder (I think it was in the "support" folder next to "icon.png" and "gog.com.shlib"), and I remember it being expensive enough that it probably still hasn't come on sale cheaply enough for me to consider buying it.
Ganni1987: Might you remember the name of that game? Only one that I know that does that is Witcher 2.
Now that you mention it, I think it
was The Witcher 2 I was thinking of. I probably got it jumbled up with my memories relating to The Witcher 3.
(When you own 1338 games on GOG alone, even a trivia fiend's brain makes the odd mistake from time to time.)
Thanks for reminding me that I DO own a game I can use as test fodder to implement support for that in my unattended unpack helper.