In 2026 the single most useful port to add to my Macs would be USB-A, with no close competition. On any device with 2+ USB-C ports, it'd easily be worth sacrificing a USB-C to get a USB-A.
Most devices have a cable that’s fully replaceable so you can choose to use C to C or C to A but basically everything has usb C on the device end.
Yes, but we're talking about the ports on the Steam Machine, so the host end is what matters. And gaming peripherals are likely even more skewed towards USB A, because Macs are not the main target for that.