So give it a network connection for initial setup then take it away?

Yeah...mine shows a nag about not accepting the online agreements, connecting the TV to the network, etc. Hasn't stopped me from using it as a display for the inputs I was using on my previous non-smart TV.

Yeah I was afraid my new TV would do that. I was planning to return it if it did because I had bad experience with Vizio and TCL smart TVs breaking updates before (I'm an Apple TV user).

I can confirm that Roku firmware works great without the internet and doesn't nag. I just turn it on and switch to my Apple TV.

Not just that. Broadband connection for things will become so cheap in the future that it could become essentially free one day so it can be subsidized by the businesses depending on it. 5G aside, It is believable that in a few years most home broadband routers, even tightly closed ones, could open a channel anyway using a fraction of the bandwidth for exclusive use by devices so that only closed source drivers will be able to instruct WiFi chips to see and use it. The catch being that there won't be any means of preventing the TV or other devices from going online, short of opening them and removing physically the network hardware. I believe we badly need alternative (Open Source, auditable, trustworthy) operating systems for smart TVs too. Next will be cars, fridges, etc. Pretty much everything.

The statement, "just don't connect it to the network" still stands. If something requires a connection, return it. It's clearly anti-consumer and will do nefarious things (which we already know Samsung does).

It was Samsung TVs that will automatically connect to any open Wifi nearby to get their ads updated, even if you tell it not to.

There are no receivers on the market that act as HDMI Ethernet network switches.

They have been for a while. But are these actually used for IP connectivity? If that was the case, a laptop’s HDMI port should show up as network interface, which it doesn’t, at least not on my machine.

Are there any examples of TVs doing this, or is this just a hypothetical?

There are some TVs that will try to connect to the internet via non-obvious means (Samsung TVs were mentioned elsewhere in this thread). TV manufacturers aren't spy agencies though. They're not going to put in that much effort to sneak an internet connection, when most users willingly connect their TVs to WiFi anyway. If I can't find an article about a given TV sneaking in an internet connection, I would be pretty confident that it doesn't.

I've been looking for years and I have yet to find any systems (TV, receiver, or injector) which actually take advantage of this feature.

This is what I did for my TCL Roku TV: just taped over the annoying blinking light.

If enough people do this, I anticipate that in the next model, they'll replace that blinking light with an forced on-screen overlay.

What is your usecase? Trying to understand the point of having apps without the wifi.

I have noticed a marked increase in youtube ads in the roku app. Prob due to roku has updated itself without permission.

Now i dread having to deal with pihole hacks + routers to fence it out of our home network :/

... "don't connect it to the network", means don't connect it to the network, via a Roku-router or wlan or whatever.

Don't buy one with other networks either, if they exist...