I have been asking since release to make the Age of Empires IV soundtrack widely available because it has only been available on Steam. While I still would like the Age of Empires IV soundtrack to be made widely available, I think that with the free DLC coming up that it would be a good idea to add the Ottomans & Malians tracks to the soundtrack DLC also for free.
I briefly discussed this with Adam Isgreen on Twitter. Please consider it!