I own Galactic Civilizations III on Steam, including most of the DLC. When I connected my GOG and Steam accounts, GalCiv3 (the base game) was successfully ported over, but none of the DLC was.

I understand GOG Connect is new and so I imagine this is a flaw in the system and one that needs to be fixed.

The Steam API doesn't report DLC owned and it had been that way for ages. I don't think GOG Connect can do anything about it.

Get in touch with support (or with the publisher) and they might manually add the DLC.

Yup, same reason there were all those issues with Darksiders 2 Deathinitive Edition.

Great Scott!

I don't see DLC on the Connect list.

Maybe this feature will be added later ?

Great Scott it is..
I wanted to help GoG so I connected my steam account, freed two games from drm and look how they repay me..

Read the second post in the thread.

A disappointing limit to the system then if GOG keeps getting more games with DLC.

I will wait for the Complete version of every game I'm interested in. I'm tired of buying DLCs one by one...

Not like it would help much - lots of complete versions are just bundles with the game... and DLC. Which the SteamAPI still doesn't report properly. Sigh.

Are you sure? Because during darksiders 2 deathinitive edition release I remember the devs claiming they can check if someone has the entire bundle but not if someone has the base game and all the individual dlcs.

Well, he said lots, not all.

Issues on STEAM or GOG? Because I don't remember reading about any issues.