Would Purism consider producing an Australian Power Adapter in addition to UK, EU & US ?
https://en.wikipedia.org/wiki/AS/NZS_3112
(BTW, I’m considering getting a Librem Mini at some time in the future. I currently have a MacBook and plan on a transition phase of dual booting PureOS / MacOS on the Mac.)
PureOS almost certainly will not boot on your Mac.
$10 on Amazon will get you a pair of US plug to Australian plug adapters. Alternatively, I think the connector into the power brick is reasonably standard (IEC 60320 C5/C6?) so if you can get the correct connector spec from Purism then you should be able to source the right power cable in Australia i.e. cable from mains wall socket to power brick.
I assume that the power brick is universal voltage, but you would want to confirm that with Purism.
That’s, in all likelihood, printed on the brick itself.
So yes, the power supplies are universal and should work pretty much world wide from 100VAC to 240VAC, so volatge (and typical AC frequencies of 50/60Hz) should not be an issue.
The “bricks” that come with the L14 laptop or the Librem Mini have a detachable cable for mains supply and use a pretty common three prong “butterfly” connector on the power brick side. It should be pretty easy to locally source a matching cable.
Cheers
nicole
So assuming that my claim of “IEC 60320 C5/C6” is correct, @ryz would want to drop in to his nearest Jaycar store and get: https://www.jaycar.com.au/3pin-mains-plug-to-iec-c5-clover-leaf-1-8m/p/PS4120 (although it looks to me that the description in the table is incorrect so I would confirm at the time of purchase) or any similar store e.g. OfficeWorks will do the same power cable if you want to pay twice as much 
https://www.officeworks.com.au/shop/officeworks/p/comsol-male-3-pin-ac-to-female-iec-c5-power-cable-2m-copcc502.
Looks like it is possible to configure a Mac to boot/dual boot PureOS, according to this: Installing PureOS on a 2015 MacBook Pro