Steam attempted this with the Steam Box, but it's difficult to do something like that in the PC market due to consumer expectations of being able to control and upgrade the hardware in your device. And doing that also made it not price competitive with consoles since the hardware makers would need to make a profit on each box sold. At which point, who is the customer for it?
I remember rumors of MS potentially thinking about something like an Xbox spec console for OEMs to manufacture and sell, but the problem arises in how to make it price competitive with other consoles (PlayStation) while incentivizing OEMs to sell it. Sharing the proceeds from game sales makes for less incentive for MS to do that but not doing that means no reasons for OEMs to do it.
Regards,
SB
For Valve I think its better to just go with a home edition of the steam deck.
When steam deck 2 launches also launch the same hardware but as a set top box like the fire tv size or a intel nuc.
Here is the fire tv for example