The iPad is missing subscribers
When deploying the final versions of iOS/iPadOS/tvOS 16 and macOS Ventura, the various systems will display the message a hub is required to take advantage of features such as receiving accessory notifications and allowing others to control your home. You won’t be able to see shared homes until they are also upgraded to the latest version of HomeKit. iPad will no longer be supported as a home hub.
This information was already within the footnotes of the official Apple website, the iPads will no longer be able to play the role of HomeKit hub/concentrator, allowing for example to control compatible devices when the user is no longer at home, sending notifications, automations or even sharing the management of a home, and will have to leave this role to HomePod, HomePod mini and AppleTV.
In the second beta of iPadOS 16, the Settings
still allow you to choose an iPad as a hub, but the option is disabled by default. Apple certainly wants consolidate the HomeKit user experience by removing the hub role from a battery-operated deviceand which can therefore no longer play its role if the user forgets to put it to recharge before leaving the home.