I had a lot of trouble getting audio/video calls to work in SimplX on iOS, compared to Signal. Enough that I and a family member gave up on replacing Signal with it because calls were worse. I’d rather use SimpleX because the security model seems better, but I need reliable audio calls, at least.
Discussion
Several problems: audio calls wouldn’t connect or ring, and video calls were… glitchy especially during the initial connection, and never did connect properly for me. I also had trouble authorizing the app to use microphone or camera for the first time in response to an incoming call. Although I DID authorize it, on both devices, so that wasn’t the problem. Things like that made me think SimpleX wasn’t ready yet. I don’t want to scare anyone away from it, definitely try it, maybe it will work for you. But it didn’t for me, to my great disappointment.🙁