The TL;DR is that the organization that controls the HDMI standard won’t allow any open source implementation of HDMI 2.1.
So the hardware is fully capable of it, but they’ll get in trouble if them officially implement it.
Instead it’s officially HDMI 2 (which maxes out at 4k @ 60Hz), but through a technique called chroma sub-sampling they’ve been able to raise that up to 4k @ 120Hz.
However there are some minor reductions in picture quality because of this, and the whole thing would be much easier if the HDMI forum would be more consumer friendly.
In the meantime, the Steam Machine also has display port as a completely issue free display option.
DisplayPort rocks
Yeah fuck the video codec mafia and all these proprietary shits like HDMI
Fun fact, all of the audio codes are proprietary too. You won’t find a HDMI surround sound splitter on Aliexpress. Say no to HDMI, say no to E-ARC.
You know it reminds me of the academic publishing mafia of Elsevier and the like
I used to find it took forever to start showing a picture compared to HDMI on my PC. Getting a new GPU so maybe that will improve things.