Well, I think it’s pretty hard to find underground artists on spotify or apple music, so you can try using something like soundcloud, there are many small artists that deserve more recognition, so I recommend you check out streaming services like this one, and I’m sure you’ll find a lot of new songs.
As for me, I’m a huge fan of various audiobooks and sometimes I download them with the help of 1377x and RARBG and by the way, if you are interested in this theme then check these audiobook torrenting sites because I’m sure that you will be able to find something reliable and nice for yourself there.