Edit: I looked it up, maybe not Australia...
I'd pre pandemic FB Messenger was definitely more popular but there's been a gradual but noticible shift to WhatsApp since.
Hmm. China? No -- WeChat. Japan? No -- Line. Korea? No -- KaoKao.
https://worldpopulationreview.com/country-rankings/whatsapp-...
Edit: I looked it up, maybe not Australia...