The Italian Dept. of Health has revised the regime relating to the inbound and outbound movements from third Countries in force starting from 16/12/21 until 31/01/22
This update involves all category D Countries like Australia.
For more information read the grey section of the following link https://www.esteri.it/en/ministero/normativaonline/focus-cittadini-italiani-in-rientro-dall-estero-e-cittadini-stranieri-in-italia/