Back in November of 2003 I worked on a Quake 2 mod called NightHunters.
The source code is avaialable on GitHub along with fixes to allow it to compile on a modern Linux system (gcc version 9.3.0+). Also available in the repository is a pre-built Linux 64bit library file that can be used with Yamagi Quake II.
To install, download nh151.zip or nh151.tgz from the Download section of the Night Hunters web site and then extract to your Quake2 folder. This will create a /nhunters subfolder with the required pak file etc. For Linux 64 bit, also download the game.so file from GitHub and place in the nhunters folder. See nhunters/readme.txt for more info.
The old web site has been archived here.