Action Quake 2 (AQtion), a free and open source first-person shooter that the developers say "spawned one of the most popular and influential games of all time, Counter-Strike" is now available on Steam.
Read the full article here: https://www.gamingonlinux.com/2022/06/action-quake-2-aqtion-considered-the-precursor-to-counter-strike-now-on-steam