The question has been asked. In light of recent papers, below is a stylized tree I drew up (the lengths of the branches don’t equal time!).
The indigenous population of Australia is at minimum a compound of two elements.
1) A very distinctive component which may have pushed out of Africa earlier than all other non-Africans. Term this the Ancestral Australians.
2) A second element which was a branch of the second wave of non-Africans, probably dominant across South and Southeast Asia. This branch, term then the Ancestral South Eurasians, exhibit greater similarity to East Eurasians than West Eurasians. Whether through phylogeny or just gene flow. In any case, the South Eurasians seem to have marginalized the relations of the Ancestral Australians across Southeast Asia, with the only non-Oceanian relic of the earlier inhabitants being the Negritos of the Philippines, who are also descended in part from the Ancestral Australians (the balance being Austronesian).
3) At some point the South Eurasian component become a substantial proportion of the ancestry of Near Oceanians, the peoples of Melanesia and Australia. The Peoples of Melanesia and Australia admixed with the eastern edge of the Southeast Eurasians.
4) In South Asia the western edge of the Southeast Eurasians, the Ancestral South Indians, mixed with the Ancestral North Indians.
In sum, the phenotypic and genetic connections which have been adduced between populations in the Indian subcontinent (“Australoids”) and Australian Aborigines must come via the Ancestral South Eurasians, whose range spanned both Near Oceania and South Asia. In Near Oceania they were almost certainly intrusive, an invasive layer over the Ancestral Australian substrate. In South Asia they were the indigenous population. The admixture event of the Ancestral South Eurasians and Ancestral Australians likely predates the settlement of the Americas 10-15,000 years before the present, because Native Americans seem to share particular derived mutations which span all populations with broad East Eurasian ancestry, including Aboriginals. The admixture of Ancestral North Indians and Ancestral South Indians probably dates to the Holocene, and may be as recent as 4,000 years in the past.