Can Australians work in Europe with an ETIAS?

No, the upcoming ETIAS authorisation does not permit Australians to work in the Schengen Area. ETIAS is not a visa or a work permit, but rather a pre-travel authorisation for visa-exempt travellers who are travelling to the Schengen Area for up to 90 days in a 180-day period for tourism, business meetings, transit, or short-term study (less than 90 days). 

If you intend to work in any European country, you will need to apply for the appropriate work visa or work permit from the specific country where you plan to work. Each country has its own entry and visa requirements and procedures for work authorisation, which may change over time. It is your responsibility to verify these entry and visa requirements with the official government authorities including the European Commission and the embassy or consulate of the European country you plan to visit.