Guide to WebRTC with Safari in the Wild, Chad Phillips, webrtcHacks, Sept 2018

Originally published in September 2018, there are updates all the way to August 2019 talking about iOS 12.x.

This article from Apple’s Webkit team is also helpful in understanding the roadmap:

In July of 2020, we’re on iOS 13.5.x, and iOS 14 is in preview.