What I meant by adding a layer 3 device is to add either another router, or (preferably) a Layer 3 switch (which will route) and put all of the other private network on it. This will allow the two networks to talk to each other while still allowing the security you are looking for. Honestly, and at least in my opinion, I would say most folks would not consider a smart TV to be part of the IoT family, as IoT devices are usually things like smart plugs, lights, wall switches, microwaves, ovens, etc...basically single function devices that do not run apps. Your TV is capable of running multiple apps (every streaming service is its own app) and has a complex operating system, unlike a "smart" plug or other IoT devices. TV manufacturers get a lot more scrutiny than the hundreds (if not thousands) of offshore manufacturers of smart plugs and the like, and this is where the security concerns with IoT devices lies. No one knows with certainty how much and what data these things are collecting and phoning home with, therefore the reason for isolating them. I would put my Plex server and all my TVs on the same network, and then isolate all your "smart" plugs, lights, light switches, etc either via VLAN or a separate network. Hope this helps?