They're usually just called "crimp rings" or "cinch clamps", the former being the more popular term in my experience. They do require a specific crimping tool, but if you go to your local home improvement store they usually sell a kit that includes the tool with rings, and possibly even a PEX cutter.
It's an angle valve for sure, but it looks ancient. Nowadays the valve would be inserted into what looks like pex piping there on the right, and you crimp a ring over the piping to get a nice tight compression fit.
The Steam Deck is already a couple of years old, so it's not that hard to do. This thing has better specs across the board, with even the base model having twice the cores and threads as the Deck.
They're usually just called "crimp rings" or "cinch clamps", the former being the more popular term in my experience. They do require a specific crimping tool, but if you go to your local home improvement store they usually sell a kit that includes the tool with rings, and possibly even a PEX cutter.