I was excited to see this headline, but it's not really true like most people will think.
This is the older (pre-Steam Deck) Linux project that was released years ago, but was (sadly) discontinued. It was Debian-based, while the new SteamOS (SteamOS 3, used on the steam deck) is Arch-based. Last I heard they are planning to expand the offering for SteamOS 3, but it's not ready yet.
I have not personally tried it, but HoloISO claims to bring SteamOS 3 (the current arch-based version) to generic non-Steamdeck hardware.