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.
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...
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.