Replacing the SteamOS 2.117 update, SteamOS 2.121 was promoted to the stable channel as the latest and most advanced version of the Linux-based gaming operating system that powers the Steam Machines, or your personal computer, including pretty much the same updated components that were available in the Beta version. However, the stable SteamOS 2.121 update comes with a newer kernel, specifically Linux 4.11.12, which appears to be the last in the series as it recently reached end of life and it’s no longer supported upstream. Other than that, there are a bunch of updated packages that fix various security vulnerabilities in the OS.