The link has a ton of information.
Now, It is obvious that putting it completely offline is more safe. But, some people often use the TV’s to watch Netflix or something like that. Then they might forget that it is still connected to the internet when they are done watching.
Under Privacy Settings, there are options for Device Usage Data, Collect App and Over-the-Air Usage, and Interest-Based Ads. All are enabled by default, but you can disable them.
I think it’s important to note that most of the devices you’ll find if you just search for a cheap and generic “Android media box” are not going to be any better for your privacy. Even if you ignore the data collection you subject yourself to with Android, you might be purchasing a botnet node or a backdoor into your home network.