Are there any Chinese, Arab or Indian maps that include Australia, for example? Did any of the Muslim traders that visited Asian islands ever sail further south? Any travel diaries?
They had knowledge of what is now Indonesia, and religions like Hinduism, Islam and Buddhism were/are popular in these areas.
Do we know anything about the extent of their knowledge of Australia?
I helped answer a similar question recently: https://www.reddit.com/r/AskHistorians/comments/668yng/why_didnt_any_southeast_asianasianpolynesian/