How's that different than just not connecting?
Because if a device can't connect, it will often have logic to try to find other routes e.g. open WiFi nets
It would be tricky to implement, but a network tarpit that responds on TCP as if outgoing packets are being accepted and routed might be useful.
I read of this tactic a few years ago. Some mentioned adding a phony static IP/gateway/DNS to avoid it connecting to open wifi(should this tech permit it).
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> Unfortunately, every few months the display tries to coax them into connecting to WiFi, and it confuses the heck out of them.
I'm assuming, perhaps incorrectly, that if the TV had a crap connection it would stop nagging.