Hi semtal14
welcome to this Apple (user-to-user) Community!
Re: "Cannot add Aqara G100 camera to Apple TV Home settings
I have purchased Aqara G100 security camera, which supports apple home".
Now, am no expert in this area, yet your post to the community deserves some response.
Fortunately, Apple provides a lot of articles with step-by-step "how-to" information.
When I checked Apple's article online: Home app - Accessories - Apple
I didn't find the Aqara G100 Security camera.listed with other Aqara Cameras.

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Re: "My all apple devices and Aqara camera is in their latest version, updated.
May be it existed some time ago or in older IOS versions"
Wondering if you have actually installed the most recent tvOS update for your Apple Tv 4k:
About Apple TV 4K and Apple TV HD software updates - Apple Support
says
the newest tvOS 26 version is txOS 26.1
the newest tvOS 18 version is tvOS 18.6
You may want to Find out which Apple TV you have or how to update it to the latest software.
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Re: "The problem is that, I can’t add it to Apple Tv 4k: I watched numerous videos on YouTube, but nothing useful. They all claim (including chatgpt) that there is Apple Home thing in Apple Tv’s settings. But it disappeared"
Have you already : Set up your Apple TV 4K on the Home app - Apple Support
else see the step-by- step info. in the linked article above
Then you may be able to:
Monitor cameras and run scenes in the Apple Home tab on Apple TV 4K - Apple Support
Good to know you could add the camera to the Home app on your iPhone ok.
If needed: See how to: Set up security cameras in Home on iPhone - Apple Support
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Resource: For tvOS 26 : Apple TV 4K User Guide - Apple Support (You can also choose tvOS 18 at top of articles)
Hope there's something useful to you here, and, at the very least, we keep your discussion thread active, allowing more opportunity for others to share their expertise.
All the best :-)