There are plenty of supposed Steam Deck killers available in the portable gaming space, from the Asus ROG Ally to the Lenovo Legion Go and all the Ayaneo and ONEXPLAYER devices in between. But none of them have managed to outright slay the dragon that is the mighty Steam Deck yet.
Honestly no idea why Valve isn’t partnering with these companies or why these companies (presumably) aren’t reaching out to Valve.
They work together. Asus and Lenovo sell hardware. Steam maintains software and sells games. Consumers get a sick handheld. Everyone wins.
Maybe Valve just wants to have a limited hardware target for game devs.