SimpleX Chat is a decentralised messaging platform offering also voice and video calls. Text and voice messages, file uploads, voice/video calls are end to end encrypted. The backend servers are mere relay servers which just store the encrypted content for a limited period of time, thus giving the opportunity for members of chat rooms to download it in the meantime. SimpleX Chat does not rely on any centralised infrastructure and does not require the usage of domain names either.
For the time being SimpleX Chat is available only on smart phones
Note that the Android app is also available on F-Droid.