We know that pure blood Garleans can't use magic, but to take it a step further are they able to use aether at all?
Magic is a manipulation of aether after all. Additionally, many (or all) class/jobs all use aether in one way or another, but they call it by different names where they're from. Ala Mhighan Monks call it "chackra" Doman NINs call it "chi" etc.
In otherwords, people use this energy (aether) to augment their abilities. So to me, it would make sense that they also can't utilize aether
It could just be plot, but I don't see Garleans using aetherytes (which requires you to use aether) within their camps. Especially when Nero and co were observing us kill primals. One instance (after beating Titan) we see Lahabrea and Yshtola teleport while Nero walked away