ArcaneChat is a FLOSS private and secure messenger focused on privacy and friendly user experience.
💬 Reliable instant messaging with multi-profile and multi-device support.
⚡️ Sign-up easily and anonymously, no phone number or any private data required.
🎮 Interactive mini-apps in chats for gaming, shopping lists, productivity and collaboration.
🔒 End-to-end encrypted chats safe against network and server attacks.
ArcaneChat is a Delta Chat client and it is compatible with other Delta Chat clients.
Source code: https://github.com/ArcaneChat/
Also another downside, if I am not mistaken, is that all of the chat metadata is unencrypted, unlike alternatives like signal. (I think this is the nature of being essentially encrypted email on the backend)