Local and (some?) state elections, sure. I voted in the NSW state election online while living in London, after having unknowingly missed voting in the previous one while in Tokyo, thereby having the state revenue service after me when I got home months later π
Federal still requires you to rock up to a polling place (usually the embassy), or postal vote.
Huh, I've not heard of this, though it doesn't surprise me.
In the area where I grew up (waaay out in the sticks, with no easy public transport access to the closest AEC office), the AEC tended to send people out to your home on your 18th birthday (or soon after it) and enrol you on the spot. This was decades ago, though, before you could do any of it online.