This seems kinda silly, but I remember someone here was asking this exact product awhile back.
To be clear, this is for just the pillow and mounting arm, which can be used with various devices. For the steam deck specific mount, you’ll also need this, or their full steam deck bundle.
Alternatively if you have access to a 3D printer, they provide most of their designs here.
Maybe I don’t play long enough sessions for this to be a concern, but I just…hold the Steam Deck. Elbows on the couch is a pretty solid mount lol.
Resting your elbows is the key there.
If I play on the couch I get the issue this solves, but a dock and a controller solve that if I must be on the couch.
This is really nice for games optimized for the touch screen such as Football Manager or Magic the Gathering. Holding the deck with one hand and playing with the other is uncomfortable after a while.
Sometimes I forget the Steam Deck has a touch screen. I definitely wouldn’t want to support the Deck one handed for more than a few minutes.