Presumably it’s just a dock with an extra M2->USB adapter, so it should work as an external HD yes. I would be weary of having an SSD without protection (shell/cover) like that.

short answer yes,

before 3.5.5 you had to run a script so that it would auto mount usb/external drives but now it will auto mount them without script. make sure your steam deck is updated to latest.

saw a review for something like that and he said getting it to work was more hassle than it was worth when the sd card slot is right there meant to be used

It’s a PCIe to USB bridge, so completely useless. Just stick another USB drive in there.

Sure. But you’re probably better off getting a “normal” dock and plugging in a USB storage device into one of the USB slots. You’ll get the same effect.