http://isdb4l77sjqoy2qq7ipum6x3at6hyn3jmxfx4zdhc72ufbmuq4ilwkqd.onion/blog/20230328-simplex-chat-v4-6-hidden-profiles.html
These calls are still end-to-end encrypted, and compatible with the calls in the previous versions of the app, both on iOS and on Android platforms. Where allowed by App Store policy, the calls on iOS now use Apple's native interface for calls CallKit, that allows to accept calls from the lock screen, prevents call interruption by incoming phone calls and optionally allows to include calls in the phone call history - the last option needs to be enabled...