It "was" public, most people missed out at the time.
NO, do not ask me where to get it, or any other information about HALO Fireteam Raven.
Use your Google-FU
https://en.wikipedia.org/wiki/Linux_Unified_Key_Setup
Just as this game.
Also LUKS encrypted partitions.
And NO, do NOT ask me about HALO Fireteam Raven.
Yes, HALO Fireteam Raven runs on LINUX !
So probably only TeknoParrot can run it, in the year 2525 !
Run game in full screen portrait mode, rotate screen before starting game.
Afaik you can change resolution settings in config files, but flip resolution around.
So 1366x768 becomes 768x1366
You probably did not limit the game .exe FPS in NVIDIA control panel or in RivaTuner.
https://www.howtogeek.com/509097/how-to-set-a-maximum-frame-rate-in-nvidias-drivers/
https://www.guru3d.com/files-details/rtss-rivatuner-statistics-server-download.html
Tried this ?