Wavelenght looks really nice but the fact that they tell nothing about themselves nor is the code open source does not send "trust us" signals.
Also, asking for your phone number when it's not used for calling + asking to send your entire contact list's phone numbers to their servers is so web2.
"Some parts of Wavelength are licensed under third-party open source licenses. We may also make some of our own code available under open source licenses."
The group chat with threads is something desperately needed though.