Someone figured out how to mount a phone to a Steam Controller, if you're so inclined.
A modder designed a 3D-printed bracket that physically attaches a smartphone to Valve's discontinued controller. The result looks like a DIY handheld gaming device — part phone, part controller, held together with screws and determination. There's just one catch: most iOS and Android apps don't recognize the Steam Controller as a valid input. The hardware works. The software support doesn't.
This is a workaround in search of a problem. Mobile gaming already has dozens of dedicated controllers with phone mounts that actually function out of the box — Backbone, Razer Kishi, GameSir. The Steam Controller was discontinued in 2019, and Valve never ported its input mapping system to mobile. So even if you bolt your phone to one, you're left with a mechanical solution and no software to use it with.
Valve's old hardware just won't die, it seems — even when the software won't play along.