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.
Biggest I found is the Acer Nitro XV275KP3 Gaming Monitor. You kinda pay gaming hardware prices, but given the support for up to 120Hz and HDR10, I was OK with that. It’s mostly used for gaming, anyway.
It used to be that beamers were a way to sidestep the “smart” bullshit, but they started adding that, too. Even the business ones.
A 27" monitor will not be anywhere near a replacement for 60" TV, I’m afraid.
That one is 27". I think that’s way too small for the living room. I also consider 120hz to be overkill for some couch gaming and movies.
Do let me know if you find something more suited.