1. install "Notifications for Android TV" apk in Android TV.
2. Browse to your Home Assistant instance.
In the sidebar click on Settings.
From the configuration menu select: Devices & Services.
In the bottom right, click on the Add Integration button.
From the list, search and select “Notifications for Android TV / Fire TV”.
Follow the instruction on TV screen to complete the set up. Just input TV's IP address.
3. create "automation" in home assistant for "sensor" trigger "action".
more details on home assistant webpage: https://www.home-assistant.io/integrations/nfandroidtv