Buying DLC from Steam for registered base game?

[Mystic]

Years ago I bought RimWorld directly from ludeon.com, but today I finally got around to registering it with my Steam library (I didn't have Steam back then, whereas now it is just about all that I use). However, I'm confused as to how I can go about buying the Royalty DLC. I'd prefer to get it through Steam, just to simplify payment, but I don't see a "Manage My DLC" link on the Steam game page, unlike with all of the games I've actually purchased through Steam. It looks like Steam will let me buy the Royalty DLC, but I'm concerned that doing so might result in it not working with my copy of RimWorld since the latter doesn't appear to be a "true" Steam purchase (despite the fact that I downloaded it anew today via Steam). Can I buy the DLC from Steam, or do I have to go through the ludeon.com website again and then do the same registration of Royalty with Steam?

[Canute]

You can do both.
Buy it over the website and register the DLC at steam like you did for the basegame.
Or buy it at steam.