STBs don't use the router for TV channels. (For sure the older models. Not sure how rotuer plays in to Quantum)
Only for guide and VOD.
You can always put a timer on the ONT pwoer supply.
When it shuts the power off, Internet and TV go down, but phone stays up for the length of the battery.
Just would need a way to lock up power connection so they can't plug it in.
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