Hey - Thanks for the response and the screenshots. Indeed, as you already mentioned, they are not going to be useful (I dont know why I had it in my head that they could be - I thought perhaps in your case the DLC's would be listed within RS 2014 and not OG RS? idk.)
To make matters even worse (or best?) I tried installing it on my Steam deck, and the RS1 DLC's show up there. At this point I already went to the point of Completely removing RS2014, moving it to a new directory, all from scratch, and still same behavior. Steam support recommended me to reach out to Ubisoft but I doubt they will be helping me with a game they don't even sell anymore.
Guess one day it will magically work? In the meantime I guess I will play the other 1000's of songs instead of focusing on the handful of missing songs ¯\_(ツ)_/¯
Thanks for the help and feel free to send any other suggestions if you can think about anything!