That's not a ITX build lol. The Lian Li is gigantic in comparison to the Steam Machine. Hell even an actual ITX case like the Fractal terra is nearly 3x bigger in volume.
Here's a size comparison of the case you posted, a Fractal Design Terra (amazing ITX case), and the Steam Machine
comparesizes.com
Ignore the fact I never changed it was inches to mm. The comparison will be the same.
I'm repeating myself, but once again, that doesn't matter. if you can fit a Steam Machine, you can fit that case.
it doesn't need to be the exact same size as the Steam Machine.
a TV cabinet either has flat+wide storage spaces, or large rectangular ones.
the Steam Machine is too big to fit into most flat+wide spaces, and the larger rectangular ones fit both the Steam Machine, and any PC the size of that Lian Li case I linked.
so if you have one that only has the flat+wide ones you're out of luck anyway. if you have larger rectangular space, both machines would fit, and in practice it wouldn't make much of a difference.
here's an example I found with a quick google search.
notice that wide space in the center. that would fit a PS5 easily, but not a Steam Machine, even tho the Steam machine is smaller. the 2 half sized ones below would of course also not fit a Steam Machine. but it would fit into that larger rectangular spot on the left that is closed with a door in this image.
and the PC I linked would fit in that exact same spot too... and would in practice barely make a difference unless you wanna cram in multiple Steam Machines sized devices in there.
I deliberately didn't go full small form factor because those are not practical. having a case of the size I linked is perfect for a machine connected to a TV, while not limiting you too much once you want to upgrade the GPU down the line.