This concern exists regardless of what device is running on the TV.
If you have a wireless keyboard that’s comfortable on the couch, use that. Otherwise, just use a controller and launch in Steam Big Picture mode (now basically looks like Steam Deck’s main screen).
Good launchers (not all of them) also take controller input.
EDIT: But I think to reinterpret your question, yes, the device on the TV generally should have the input connected directly. That can be done with Android TV and I think Apple TVs.