I think Google Duo and WhatsApp are the competitors to Facetime. Zoom is more of a competitor in the video conferencing space along with Google Meet, Skype for Business and Cisco WebEx. Regular Skype is more of a competitor in the all-in-one consumer messaging space along with Google Hangouts.
Unfortunately all are proprietary and it was the previous generation, iChat and Google Talk, that were based on the open XMPP standard.
Unfortunately all are proprietary and it was the previous generation, iChat and Google Talk, that were based on the open XMPP standard.