We use Wire. In some respects it's more useful than Signal, because it works on mobile, desktop and web. I think the desktop clients are Electron based, so I use the mobile and the web apps. You don't necessarily need a phone number, it can also use an e-mail address, so it works just fine on the desktop. It also has voice chat and conference. Oh and a good part of it is open source, although it's uses a centralized server.

I second the Wire recommendation because you can sign up with an email address, and conversations sync across devices. Its feature set is also good (not as good as Telegram) and improving. I wouldn’t recommend Signal as it is still poor in features, speed and stability.

With Signal you cannot carry your chats to a new device (this is prohibited by design in the app on iOS)!

If you want to experiment, try both Wire and Signal at the same time, and you’d observe the differences quickly.

I personally love Threema [1], which is available for iOS, Android, Microsoft and Web. It uses a random ID to identify users, uses End-to-end encryption, you can make voice calls, send messages, audio messages, GIF’s etc.. Oh, and it has a dark theme!

Please note that Threema is not open source. If you want that go for Signal instead.

[1] - https://threema.ch/en

Signal is probably the best combination of easy-to-use/secure.

Signal doesn't support vcard which makes it a non-starter for many people [0][1].

[0]: https://github.com/signalapp/Signal-Android/issues/6520#issu... [1]: https://github.com/signalapp/Signal-Android/issues/6520#issu...

Interesting comment. How frequently do you think this one vcard-related issue you linked to is a problem for Signal users trying to share contact information with each other?

And could you give an example story illustrating how two users would run into this issue in practice?

My parents & siblings are a mix of android/iphone users and I convinced them to all join Signal for group chats and it's been very solid.

I would use Signal, quite simple and privacy focused.

I'd recommend quicksy if she's really clueless. It's an xmpp client that uses the users phone number as identifier and does autodiscovery with the users address book to check if any of their contacts are registered too. That functionality aside it's still a fully functional xmpp client, so you can talk to her with conversations, gajim, dino etc if you want.