The HDMI Forum, responsible for the HDMI specification, continues to stonewall open source. Valve’s Steam Machine theoretically supports HDMI 2.1, but the mini-PC is software-limited to HDMI 2.0. As a result, more than 60 frames per second at 4K resolution are only possible with limitations.
Got a Firewire port on my PS2. The only thing I’ve ever owned with Firewire and I never even used it.
I have an old iMac that I use as a Plex server, and it has a firewire 800 port and a thunderbolt 1 port, both of which I use for a couple of very old external drive enclosures. Sure as hell beats USB 2.0.