Signal is a cross-platform centralized encrypted messaging service developed by the Signal Technology Foundation and Signal Messenger LLC. It uses the Internet to send one-to-one and group messages, which can include files, voice notes, images and videos. It can also be used to make one-to-one and group voice and video calls.
Signal uses standard cellular telephone numbers as identifiers and secures all communications to other Signal users with end-to-end encryption. The apps include mechanisms by which users can independently verify the identity of their contacts and the integrity of the data channel.
Signal's software is free and open-source. Its clients are published under the GPLv3 license, while the server code is published under the AGPLv3 license. The official Android app generally uses the proprietary Google Play Services (installed on most Android devices), though it is designed to still work without them installed. Signal also has an official client app for iOS and desktop apps for Windows, MacOS and Linux.
Pros and cons⚑
- Good security by default.
- Easy to use for non technical users.
- Good multi-device support.
- Uses phones to identify users.
- Not available in F-droid.
I'd first try to use signal-black.