

You can use pretty much any smart TV dumbly. The most obvious way to do so is to just not connect it to the internet, but if you want it on the network for certain things (like home automation), just don’t agree to the bullshit when you first power it on, create a login, or enable any of the ad-tracking junk disguised as features like “live TV plus” (which is often hidden across multiple menus). The Home Screen for it will forever look like a generic menu begging you to configure your TV, but if you have other stuff plugged into it you’ll hardly ever have to see it.
To really be sure you can use a raspberry pi running a pi-hole server to see if it’s phoning home at all. My LG does nothing online except when I have it pull an update in the rare instance that one comes out with an improvement I care about.
Using a digital signage screen is an interesting suggestion that comes up often, but if you’re a home theater junkie you might have trouble finding one of those at the same level of quality as the best smart TVs at a comparable price. There’s always a trade off to find between what you’re looking for, what you’re willing to deal with, and what you can work around.

Not an issue I’ve seen with LG at least. Their OS is bad for the reasons I mentioned (apart from perfectly good standard “dumb” TV controls), but the hardware is great.
A TV just bricking basic functionality because it’s not on the internet would probably be grounds for a class action lawsuit here.