They do, and they let you install your own OS.
https://www.steamdeck.com/en/software
> The new version of SteamOS is optimized for handheld gaming, and it won't get in your way with other stuff. But if you want to get your hands dirty, head on out to the desktop.
And https://www.youtube.com/watch?v=oLtiRGTZvGM has a Valve engineer it's more accurate to view these devices as PCs with custom controllers, and that you can install your own OS.
This is pure speculation on my side and I really hope I'm dead wrong but that's the first thing that comes to mind when I think about it (also, their own DRM right?).
Edit : the reply bellow seems to prove me wrong =)
>You can also install and use PC software, of course. Browse the web, watch streaming video, do your normal productivity stuff, install some other game stores, whatever.
and
>The default Steam Deck experience requires a Steam account (it's free!). Games are purchased and downloaded using the Steam Store. That said, Steam Deck is a PC so you can install third party software and operating systems.
Definitely. I have a Steam Link and you can enable ssh access to the root account by simply plugging in a USB flash drive with a particularly named text file and rebooting.
valve so far has been miles better than any other big DRM platform. i would almost bet valve will let you have root on these and do whatever you want with the hardware without any jailbreaks. It may not be supported, but I really cannot imagine them locking this down. That would be very much unlike valve.
iirc steam machines back in the day did also let you go into a bash shell?
full disclosure: i may contain traces of a valve fanboy.