Unpopular opinion, perhaps - isn't this just tech looking for a problem to solve?
The fact that the apps I would actually care about having on real estate on my front room seem to be nowhere to be seen is kinda glaring from my perspective... I know there's a certain purism to having Firefox front and center... But really?
I'd argue that that's orthogonal; this is making the general UI work well on a TV, then apps get populated into that. And honestly I'll bet that for most uses Firefox working well is what you want, since a handful of shortcuts to open Firefox to assorted streaming services would do the trick quite nicely.
I immediately envisioned having my feed reader as a FireFox shortcut and being able to navigate to YouTube videos from that.
Another thing is that I've found certain old movies can only be streamed from weird websites - as in https://weirdstreamingwebsite is the only licensed entity to have it. I could either buy a VHS (which is what we did) or stream it. But since a physical copy might not be available, the only option would be to use that weird website to stream it. There is no app!
The fact that the apps I would actually care about having on real estate on my front room seem to be nowhere to be seen is kinda glaring from my perspective... I know there's a certain purism to having Firefox front and center... But really?