Quake II soundtrack is still in some sort of copyright limbo. It's easy enough to find on Youtube, but it's not on streaming services as far as I know.
EDIT: maybe it's getting sorted out, there's even a fricking vinyl release
Quake always had amazing soundtracks. Nine Inch Nails "nailed" it on Quake 1. Quake 3 soundtrack is dope as well, but my all time favorite is the Quake 3 Rocket Arena vibes:
https://youtu.be/clkOT6vRKDg
I was a bit annoyed when I bought Quake II on Steam a few months back and found it didn't come with the soundtrack. I just grabbed it from archive.org and dumped the files in the right folder, worked fine.
Presumably this is a general comment, since this release does not (and wasn't intended to) include any of the Quake II models, levels, graphical assets, sound effects, or music. It's purely engine source code.
If you use Spotify, you can actually find the Quake I soundtrack under Nine Inch Nails. A real blast from the past. Quake was my first FPS with multiplayer, and I hogged the only telephone line my family had, so I could play mods like capture the flag, including the grappling hook. This was also around the time I started exploring Linux with Slackware, and dialing into my local university professor's Linux server to build web pages (before CSS was even available in browsers). Those are my favorite days of the internet, although it was much slower.