I tried Jami for a bit with a friend. For both me and my friend, Jami was very unreliable about delivering notifications about new messages. So my friend would send me a message but because I didn’t get any notification about the message it would go days before I opened the app and saw that he had said something, and I’d respond to it and it would be days before he would happen to open the app again because he also didn’t get any notification.
I never had that experience because I never found another person with Jami.
This is sadly a ubiquitous problem with FOSS phone software. Google's and Apple's notification systems are anti-FOSS. You can use your own on Google phones, but then your app will have to wake up periodically to check it, and the system will detect your app as a battery waster, tell the user your app is a battery waster, and automatically prevent your app waking up to prevent battery waste. And on Apple I believe you simply can't do that because they user has to open the app to wake it.