MarkoH01: Since I got this game gifted on GOG two days ago I tried to use the steam executable with the GOG version of the game. Unfortunately the game does not start anymore after that. So it's not that easy.
AmethystViper: What about replacing the GOG data files with the Steam files but use GOG's executable? It has to be the files that somebody at Nordic/Gunfire Studios/Vigil Games screwed up with the GOG version and maybe using data from the Steam version might fix the former.
Tried it and it works. The prompts are shown and I noticed that the prompts are looking different than the ones the game showed in the GOG release prior to patching. However I don't know what we have acieved now. The datafiles are far too big to share...
Edit:
In fact apart from the executable there are only three files in the steam version that differ from the GOG version:
media.upak (about 7GB)
scripts.obsp (about 17MB)
worlds.bin (about 32MB)
tried to shuffle around the smaller files but this is breaking other things (menu descriptions i.e.)
I have also written Nordic today telling them what I think of their "money now - fix game laaaaaater" policy.