The user must choose in the settings of each channel and group what should happen: whether the Telegram should delete the group/channel or transfer to heir in a list of possible heirs created by the user
I like those options. Simple, common sense, and avoids the issue that not all admins are desirable owners.
This is very necessary, because if the owner of the group is no longer active, then the group will be abandoned. Therefore, there should be an option for group admins to be able to claim group ownership.