Really what it should be is:
- a "remote" multiplexer comes in the box with my TV. It speaks HDMI/CEC to the TV telling it what input is active so that the TV's UI can reflect that and it can do things like switch between movie and game mode picture tuning.
- the former AVR should become a purely eARC box with no buttons, not even a power button— it comes on on command of the TV, and adjusts its amplification volume according to the same eARC signals that a soundbar uses. Any initial calibration or speaker setup is done via a single-use phone app.