free chat app with end-to-end encryption operating on Android and iPhone

Question

What I need is a chat app with the following features:

• Has end-to-end encryption.
• No mandatory monthly / licensing fees. In other words: a free public service.
• Mobile app supporting both Android and iPhone platforms.
• Group chats that are easy to manage (add/remove contacts to/from), join/rejoin and persistent. This latter means the opposite of how Skype for Business handles group chats - a person should be able to get back to an estabilished group chat five minutes after purchasing a new phone and installing the app.
• Ease of use.
• Option to mute conversations (no notifications) is nice to have.
• Supporting a web platform is nice to have.
• VoIP / conference calls are not really required, just nice to have.

Answer 1

Signal is another example of such app, which is commonly used.

• encrypts communication end-to-end
• it's free
• has Android and iPhone support
• group chats are supported

etc.

No web app (which Telegram has, for instance), but there are desktop apps for various systems and it's also more secure than other alternatives by default, as it encrypts everything, including metadata etc. It's also fully open source, unlike e.g. WhatsApp.

Answer 2

Whatsapp will do all of this and more. And it is free.

Screenshot of website