I tried checking for update from the Controller, but it also says no firmware updates are available for this Australian device. Shouldn't this work?

same here, i can't see the firmware listed in controller.

@Bonesoul checking the part numbers from the supplier, it appears the gateway & switch h/w is same as "UN" United States model, and Wifi is "EU" European model. It may be possible to using firmware updates from the websites from those regions. But I can't be sure there aren't localisation changes for Australia. We shouldn't have to do this, Australian products should received security updates via the Controller and/or TP-Link Australia website. Or at least instructions to use firmware from another country's website. Hopefully someone from TP-Link will clarify.

Thanks @NeilR_M! I was able to install the "UN" firmware.

The Australian support site is not just missing this firmware, it doesn't seem to have been updated for any firmware for about a year. If there is no one to maintain the Australian website, maybe it should just link to the global support site?