Wickr

Wickr is a free and open source anonymous, fully-encrypted and ephemeral messenger application. It also delivers VOIP and video calls. It was bought in 2021 by Amazon.

It is available on desktop: Windows, MacOS, Linux, and on mobile apps: Android and iOS.

8 secure encrypted messaging and video call apps (2021)

Comparison of messaging and VOIP services: Signal vs Telegram vs Threema vs Wickr vs Wire vs Element vs Keybase vs twinme

Wickr vs Signal: Encrypted messaging and Voice over IP

Wickr me is a real anonymous and fully-encrypted messaging and Voice over IP, contrary to Signal which is not anonymous.