In my experience, in most countries (and outside the US especially) WhatsApp has already won the network effects battle, and it's the default messaging app in any smartphone.
Even people with iPhone will all have WhatsApp installed.
It's the default form of mobile communication here.
https://rocketbots.io/wp-content/uploads/2019/03/AppMap_5a9b...
(Whatsapp, WeChat, and KakaoTalk respectively.)