Southport in southern Queensland became a port of entry in May 2017 on a trial basis for 12 months. The trial period will end in May 2018.
At the time of writing this (February 2018) the Australian Border Force were unable to confirm if the port will become a permanent port of entry or if it will be closed at the end of the trial.
If you are thinking of clearing in at Southport be sure to confirm that is it still an approved port of entry with the Australian Border Force at the time of lodging your advance notification of arrival.
The Down Under Rally website has information about ports of arrival here :