Dundeedore
Hogwarts Express would be a road train plowing through the outback while Harry and Ron are flying in a stolen Holden UTE before crashing into the Whomping Eucalyptus
The level of danger of the same magical creatures they introduce would be baseline and wholly unimpressive.
Aus has stricter child protective services than UK, so Harry would have been moved and presumably killed by volde’s boys.
So there literally wouldn’t be a “Harry Potter” book.
Also, Aus has so much empty land, they could easily have half the country be a magical land without anyone noticing.
The “forbidden forest” would be ALOT bigger.
Evil emus.