Keybase

Keybase is a messaging app that lets you communicate with anyone even if you don't have their telephone number or email address. All you need is for the other person to be using Keybase as well.

In order to correctly sign in with Keybase, you need to verify at least one user account on one of the following social networks: Twitter, Reddit, Facebook, Github or Hacker News. To do this, you have to publish a messages (provided by the app) on the indicated network.

From this app, you can send text messages and share photos with any other Keybase user, as well as between different devices. You can also manage your storage of private and public documents. In the setup options, you can also manage notifications you want to receive and the devices you want to use.

Keybase is a must-have app for anyone who already uses this service (also available for Windows). Plus, it's open source, free to use, ad-free, and offers much more than a simple messaging app.