Was it a Windows version or DOS version?

Return to Castle Wolfenstein is Windows. Using the Quake 3 engine.

And there was an official Linux port. Which no longer works properly.

Oh boy, I don't know how I missed that detail. Sorry!

The multiplayer version got open sourced and there exist a contemporary project to keep it updated, but also as backwards compatible as is possible.

https://www.etlegacy.com/

- https://man.archlinux.org/man/aoss.1.en

- https://man.archlinux.org/man/padsp.1.en

Many old games work better under Wine than under modern Windows though.

FWIW you can use OSS-to-ALSA wrapper and sound will work.

In general you can get most of old Linux stuff to work if you find and install the relevant libraries, the main issue is that these libraries tend to be spread all over the place and sometimes even conflict with existing libraries.

With Windows you also need to do something similar with older games (e.g. use dgVoodoo2 to play old Direct3D and Glide games) but since Windows comes out with a lot more stuff and that stuff tends to be backwards compatible for the most stuff, there is much less to worry about.

Sometimes, yes - whether that wrapper's improved now I don't know, but at the time it wasn't sufficient. I found a forum post somewhere at the time which included some kind of deep library patching magic - it worked but I rather doubt I'd be able to find it again now.