This is a great game I recommend at http://www.xonotic.org It's free to download and is very stable throughput gameplay. Just download the zip at their website and follow these instructions to running the game on macOS Mojave and lower.
Blaguou Wrote
1. put the Xonotic folder in Application Folder.
2. right click on Xonotic.app
3. Click show package content
4. go to Contents -> MacOS
5. Open a terminal window
6. drag and drop xonotic-osx-sdl in the terminal
7. type enter
8. the game should launch without error
as recommended by the user https://forums.xonotic.org/showthread.php?tid=6748&pid=83752#pid83752
Blaguou Wrote
1. put the Xonotic folder in Application Folder.
2. right click on Xonotic.app
3. Click show package content
4. go to Contents -> MacOS
5. Open a terminal window
6. drag and drop xonotic-osx-sdl in the terminal
7. type enter
8. the game should launch without error
as recommended by the user https://forums.xonotic.org/showthread.php?tid=6748&pid=83752#pid83752