In that case, the only hope you have is play the cat and mouse game and hope they give up before you do. Realistically though, they probably won't bother escalate past this point because the people who would go to such lengths are a tiny minority, and going after them don't make business sense.
>If you've got logic to connect to nearby open Wi-Fi, why wouldn't you also use it as a fallback if the primary Wi-Fi is down?
One idea to counter this would be to use something like this[1] to deauth the TV instantly, or spam a bunch of open networks so it gets stuck trying to connect to those rather than actually working ones.
The problem is that putting up with this doesn't actually send a message to the manufacturer that this is not OK, so they'll just keep doing this and perfecting their malware-like techniques until it's completely unblockable without some military-grade signal jamming equipment.
Even if it can be blocked, I don't recommend anyone buy these and look for alternatives (commercial displays, old second-hand ones, https://ironcast.tv, etc)
Even if they don't do this yet it's only a matter of time before the manufacturers catch on and start doing so.