Wyvern Crown module for linux appears to just be 1 MB in size. I downloaded it anyway and ran the installer. It doesn't show up in my list of modules. The Windows version is 366 meg.

Is something broken?

I get the feeling your installer didn't download right, or it's a downloader stub.

Perhaps, but when I look at the file from the game page in my library, it is listed as being only 1 meg in size. When I download it, that seems to be the case. If I switch the System menu to Windows or Mac the file is 300+ meg.

Some DLCs were already included in the base game.
The "DLC installer" just turn on the option for you.

I know some games and some Linux ports use this trick.
But I do not know if NWN:EE work like this.

Yeah, I had the same thought, but it's not in the list of modules. I'll fire off a support email, see what happens. Maybe I'm doing it wrong.