I bought a Viseo TV and although it's possible to use it without giving it WiFi and using their phone app, they make it pretty painful. Let me explain. Every so often the TV decides to switch inputs to the one that requires WiFi. There's nothing you can do but wait for the minute or two until it times-out. The remote they provide has on/off, volume (don't use because the TV is being used as a monitor only), and input select.
On the subject of controlling household items, I have a 1995 laptop with some X-10 PC software which was probably written in the 1980's. So for timer function, that, paired with the X-10 console, which gets the program over RS-232, solves that automation. There are X-10 battery operated remote controls, but I don't really need that. None of this requires data leaving my house. I probably could rig-up an app that connected to a local machine on my WiFi to manage X-10 if I wanted to. The point is, unless you want to control something from your phone when you are on cell data, you could have a local controller running and that would not need to have any open ports to the Internet. I have a BP meter that has a Bluetooth connection and I've prohibited the app from data access and it still works, but my bathroom scale, nope...the quickest way from the scale to the phone is through The Netherlands, apparently, LOL!
I've written a few mobile
apps over the years (one of the first iPhone apps even) and it’s very rare that new apps reach back more than a bare minimum amount of OS releases.
Newer OSes have new APIs that either allow new functionality or make it much easier to build parts of an app. Going way back is not only no fun for the programmer, but takes an inordinate amount of time and effort - often you have to duplicate functionality that comes for free in the newer OS.
It’s just not cost effective to do so. Yes, you lose a few customers, but not many.
I've written and maintained apps on the Apple and Android stores and I agree that it's a pain to support old hardware, but the reason it's a pain is because they keep changing the requirements. The Apple example: Only apps built with the latest IDE are allowed on the store. The latest IDE only runs on new OS. New OS won't run on older, but perfectly functional hardware >> new development machine must be purchased. Android isn't as bad with development machines, but they keep knotching up the oldest OS version they support on the store; you can require newer, but can't go below their minimum.
If both people in the conversation have HD voice quality it is stunningly good. Sounds like you are in the same room but with no background noise. Sounds so good it sounds fake.
It's the lag, which depends on your latency, that's the problem. Back in the wired phone days, you could talk much more naturally on the phone. Nowadays, I find myself needing to fall back on my radio conversation technique... saying "over", when I'm done with a thought.