The first time I went to Australia I entered with my South American passport and a paper visa on the passport. About 5 years later I moved to Australia to do my masters, but by then I had acquired EU citizenship via my grandfather. Now, almost 10 years after living there as Italian, I live in Sweden and married a Swede so I now have a Swedish passport. I'm planning a trip to Australia next year. The question is, how many eyebrows will it raise if I enter under a third nationality? I can't travel as Italian anymore since I do t have that passport (2 EU passports seemed like overkill). Should I contact the embassy in Sweden and register in advance or something similar?
No, just register your Swedish passport online for free, and you're good to go.
Go to this site https://online.immi.gov.au/lusc/login
Create an account
Click on "New application"
Under "Application group", select "Visitor" and then "eVisitor (651)"
Fill out the registration form and then click "sumbit applications"
You'll get a confirmation email within 15-20 minutes that the registration has been successful. Then simply take your passport and go to Australia.
Pro Tip: you can now use the Smartgates as a Swedish passport holder. It's an automated border crossing system which is very easy