You will need to talk to an accountant in Australia about your tax obligations. But I think you are confused about GST. If you are an Australian tax resident it is your obligation to pay GST (if it needs to be charged), and Upwork does not pay GST on your income.
Perhaps you are confused because Upwork charges Australian GST on its own income from you (that is the GST that is shown on your invoices from Upwork).
Secondly, in general, you have to pay personal income tax on your Australian income, if you are an Australian tax resident. That is completely different than GST. Generally, you need to pay both.
There is no comprehensive tax documentation available anywhere online, because it completely depends on your own circumstances, and this is what an accountant is for.
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