But other than through unofficial modding how many of those expose an open BSD environment? The Steam Deck has a desktop mode as a selling point which functions exactly like a Linux desktop.

That desktop mode is very inconvenient to use in handheld mode so the vast majority of users use it only to apply fixes to specific games, install emulators and the like and then switch back to the Steam GUI asap.

It's very inconvenient at first.

I've had mine for about a week now, and am using it more than I use my laptop. The "desktop" mode works more than well enough for web browsing and such.

The biggest thing that changed for me was learning that you can use both trackpads on the keyboard at the same time, and use the trigger buttons to "press" a key - or to press shift if you use the opposite trigger from the side your finger is moving.

Linux actually ships on Deck. FreeBSD kernels do not ship or likely even run OOB on Playstation hardware.

FreeBSD kernels ship and run on PS4: https://en.wikipedia.org/wiki/PlayStation_4_system_software

Not sure about PS5.

> The native operating system of the PlayStation 4 is Orbis OS, which is a fork of FreeBSD version 9.0 which was released on January 12, 2012.[6][7]

That doesn't mean it's running BSD. For example, MacOS runs a non-BSD kernel with lots of BSD networking code added on-top. It is not a BSD-based Operating System but it does use BSD code to create it's environment. I would not for a single second believe that the PS4 runs an unmodified FreeBSD kernel. There is just no upstream code to support this claim.

The Deck can be compared to a laptop computer with specialized controls and a touch screen. It runs a desktop OS, with desktop programs and games. You can use it as a normal desktop computer, connected to a screen and peripherals, and this is by design.

The same can't be said of the PS; the PS isn't a desktop computer.

They don't boot into desktop linux though.