I downloaded the ultimate edition a few days ago, and to my surprise none of the DLC has been installed.
Awakenings isn't there either. Even after downloading the Bonus DLC Hotfix nothing has been added.
I'm completely lost. What do I do?

Probably this one is worth of reading (TL;DR it may be due which under which user the game was installed)

I had to verify the game files, which installed all the DLC. But now after I play, all the DLC vanishes and I have to verify the game files again. I've never had a game do that to me before.

That is a very bizarre behavior :( and far away from my experience

I haven't seen any sign of the DLCs either. I've already tried repairing the installation, but still nothing. This is the second GOG game I've bought recently that either didn't work, or have all of the promised content.

Hey so after perusing the forums for a bit, I finally stumbled across this post, which mentions running the game as an admin (assuming you're not currently playing it on an admin account).

If you open your installation folder, go into the bin_ship folder, you can right-click on the DAOrigins.exe file and toggle the option to run as administrator. Doing so finally made the DLC appear in my installed files list.