Is it halal to live on occupied land like in Australia where they displaced and colonised the Aboriginals? Is permission needed from the Aboriginal tribe leader?

If you have certainty that the land that you are living on is someone else’s personal property then this would be the case. The aboriginal people can’t lay claim to ownership of 7.9million km squared.
Neither can the Australian government, but because they are the ruling body, you must abide by the laws.