Although you appear to have already conducted some proceedings from afar, with some success?
People typically need formal case-specific legal advice about whether or not they in particular
have grounds to appeal (from afar) a substitute service order.*
Consider that the court may well have already considered questions of mere want of jurisdiction when making it.
..I no longer have any assets in Australia...
Even if true, that's not relevant to the question of the existence at law of the debt.
Nor does the plaintiff have any reason to believe you, just because you say so.
(...people also try to use physical absence from a jurisdiction to evade Discovery and Examination In Bankruptcy...)
Much depends on scale and relative costs, and cross-jurisdictional arrangements, of course.
As to futility, what happens next is typically a choice for the purported creditor.
One thing that may inform their next move is the size of the debt.
They might make different choices if it's remnant phone contract of a few hundred dollars,
compared to an unsecured person-to-person debt, or compared to it (purportedly) being a commercial debt of significant size.
Another thing that may inform their choices is the relative cost of running the claim again.
The cost of running it, and then doing overseas enforcement, versus the value of the debt, or of any future judgement debt, may not make sense.
It might also matter who the creditor is.
Government, (say, for a tax, or Child Support debt, or a Centrelink debt), may have deeper pockets, and more determination, than a private creditor.
As to you and futility....
You cared enough to go to the trouble of getting the default judgement aside.
You cared enough to come here, looking for ways to evade electronic substitute service.
It seems odd to me that that you seem set to choose evasion over defence.
It is however, your choice to make.
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* That's what Flo-Rida did in
Mothership Music.