I am obviously doing something wrong.
I bought the DLC today, but I am not able to use it.
I don't use Galaxy (since I am running Linux), I simply downloaded the (tiny) .pkg-file.
Dysmantle runs perfectly fine, and has done so for many months.
But how do I activate/install the Underworld DLC?
I tried copying the .pkg-file to the game directory, but that does not change anything.
Any suggestions? Am I overlooking something?