But they all get abandoned or suck at launch to begin with.

A streaming 4K dedicated device is about 20 to 40 dollars, which always seem to work better then whatever a console offers and for longer.

I see no advantage to have a steam cube with it.

That said, I did put Plex and jellyfin on my steamdeck so I could watch my own library while flying, so I suppose you could add either of those to the cube. They launch as just another game by the way.