https://wccftech.com/steam-machines-were-a-really-good-idea-along-the-way-to-the-steam-deck-says-valve/

When Valve announced the Steam Deck, its concept of a handheld gaming PC, many couldn't help but think back to the Steam Machines.

Announced in September 2013 and ultimately released in November 2015, these were prebuilt small PCs that ran Valve's SteamOS and came with the Steam Controller. Initially, Valve garnered support from various PC vendors such as Alienware, Origin PC, Zotac, and Maingear; however, most of those had already discontinued Steam Machines by the end of 2016, and it is believed that fewer than half a million units were sold in total (although Valve never released official sales figures). Even Valve itself eventually removed Steam Machines from Steam back in April 2018.