I can enter cheat codes into the chat console, but they do nothing.
Has anyone successfully used cheats in this gog version? Thanks!

I've checked it for you and yes, cheats are working. Hit the Tab key and enter the cheat command.

Thanks for testing!
I had tried to add an amplifier stone to my inventory (as a substitute for one that I missed earlier), but to no avail.
Don't have the game installed anymore, though.