I thought I'd recheck some of my old research on this topic, and see where you could conceivably have Austronesians settle Australia ('Oz'tronesians!)
Based on a website for commercial banana agriculture, it looks like Lakeland in Queensland is about as far north as you could have an Oztronesian agricultural package[1]. North of that, it seems, the soil is just too infertile to work for agriculture-ruling out permanent settlement by the Austronesians who sailed to western Indonesia. Going south, based on the southern limit of where one can grow the staple crop of yams in Australia, you could have Oztronesians as far south as Sidney [2]-well over hundred miles of where I put their southern agricultural frontier in my timeline on the subject. Guess I underestimated them! I think they could, in theory, expand even further south if they got sweet potatoes somehow, but that would involve them continuing *very* long distance trade over multiple millennia with Polynesia, which seems unlikely.
That's a pretty wide region that their agriculture could work, but hitting that region is difficult. I've already gone over how sailing with the wind to Australia is contrary to their practice for voyaging; while it's possible to farm on the Australian east coast, any Polynesians would probably look for very specific bits of land-access to deepwater to hunt dolphins and fish tuna (bit of a problem with the Great Barrier reef), reliable fresh water, defensible, etc. Even if they find land that matches their specifications, they will probably have to fight Aboriginal peoples to settle there, and its just easier for them to sail east and settle uninhabited islands.
Still a fun idea though. Someone should revisit it.
[1]
https://abgc.org.au/our-industry/
[2]
https://stellinamarfa.com/vegetables/can-you-get-yams-in-australia/
[EDIT] I forgot that you
can grow Austronesian crops in northern Australia, though with everything I've read about the region I don't think you can necessarily scale it enough to really make agriculture worth it.