The desktop is the best streaming box only if:

- You run Windows because nothing else will let you stream in 4k

- You ignore the absolutely sub-par UI/UX couch experience

And I say this as someone who's been running a media center pc in various forms for decades.

I use a projector as an output device (though there are plenty of TVs (just maybe not the newest ones) that still will take an input cable and blindly pass through the contents) as well as having a little wireless mini-keyboard the size of a remote with a touchpad on it and a wireless any-surface mouse that I use to control it from the couch. I genuinely don't think most people would find that interaction disagreeable and it provides a very familiar UX that you can even trivially replace or get multiple of since it's literally just a mini wireless keyboard and mouse which cost you all of maybe 30 USD.

I will conceded that windows is a real advantage though since enshittification has driven other environment applications to become rare or unmaintained. Though I haven't invested real time into seeing what options might be available as unified platform solutions in other envs - like maybe the work Valve put into proton allows you to sneak your way into good media support?