This isn't really a question that's possible to answer as written: Austronesia is a huge and very diverse region (in fact, off the top of my head, I'm not sure I've ever seen it referred to as a region rather than a language group before), but there are a couple of older answers here which you might be interested in about some different regions.

u/PangeranDipanagara answered about warfare in South Sulawesi here.

I have an answer here about Māori warfare in the 1820s and 30s that has some stuff about pre-European warfare. I have another answer here that has more stuff about pre-European Māori warfare, and also a little bit about Tokelau and Mangaia in the Cooks (though that's about the limit of my knowledge of those places). That one's a bit of an unedited first draft, but the sources are probably of interest.

edit: actually Tahiti rather than Tokelau: the Tokelau answer was here

Anyway, despite the range of locations, that's still a very tiny snapshot of the entire region of Austronesia.