[Android Apps and Games] gebxda:
Sorry for the late response. I'm compensating with a detailed explanation.

TL;DR: You can disable "Chromecast built-in" app to stop (Google's) screencasting (or screen mirroring) "guest mode", and some Bluetooth apps to disable permanently bluetooth altogether in a reversible way on your Android TV (depending the firmware).

1) About "Guest Mode" in Chromecast built-in:

(Joking mode on) So, the big G in their infinite wisdom enables by default on Android TV with "Chromecast built-in" the "guest mode". What is it? A "marvelous" mode that opens wide your Android TV to ANY device in the Google ecosystem, bypassing your Wi-Fi security in a "device-to-device" connection for screencasting / screen mirroring.

It may not be as dangerous as it sounds but, at minimum, is VERY ANNOYING.

So, what is the "official way" to disable this and prevent your idi-- -ahem- "friendly" neighbor to cast to your TV by accident and interrupting what you are watching?

Of course you may think that there is a setting, or a hidden advanced setting, something in "developer options" perhaps... No-no. The official way to disable this thing is by installing Google Home App in OTHER device an do convoluted steps to disable "guest mode"... Amazing.

Don't get me wrong, I love to be able to customize Android TV, side-load apps, etc., and vs other TV firmware and Operating Systems Android TV is the best, but I hate dumbing down options without the proper advanced settings for those who like customizing their devices and prevent this kind of things to happen.

What can you do without installing that home app in other device? Well, if you don't use screen casting (that's my case), you can disable the "chromecast built-in app" from the system itself or with ADBTV if your firmware doesn't allow it.

If you are as me, and don't want a thing unnecesarily opening your device to the world, you can disable "miracast" module and other screen casting apps from the TV vendor that come with your TV firmware too...

2) Let's talk about Bluetooth now. This one may be the fault of my TV manufacturer (TCL) and not Android TV per se.

In my case I have separately "bluetooth activation" and "bluetooth discovery". At surface it seems as a very smart move: you could pair your devices and then disable BT "discovery" to prevent other pairing attempts... Right?

Well, no. Not only bluetooth itself reenables automatically, but discovery too. You have NO PERMANENT SETTING, no advanced or hidden setting either, to only enable discovery manually and when you want to, or bluetooth altogether.

So, how to prevent your "amazing" neighbor from trying to pair to your device in the middle of your movie time?

If you use bluetooth for headphones or something else, you can download "bluetooth discovery disabler". This is a fast way to keep controlling and disabling bluetooth discovery everytime you turn on your TV (but is not a permanent solution).

If in any TV you don't use bluetooth at all, and you want to disable it permanently in a reversible way, but the firmware of your TV doesn't allow it, in that case comes ADBTV to the rescue, as in my Grandma's TV.

You can disable bluetooth apps and system bluetooth apps, and bluetooth wil be disabled PERMANENTLY (even when rebooting your Android TV), and as I said, in a reversible way.

So, ADB and ADBTV are the best next thing to rooting when that is not possible, as with Android TV.

The great thing about Android TV is that you have the option to use ADB, and I hope it keeps being an option in the future to be able to debloat your TV and customizing it to your liking.

Now, thanks to ADBTV I have a fast Android TV experience, customized to my needs in my Family TVs.