I am very pleased with the update from @signalapp which means that you can now generate a username and not have to publish or give out your phone number.
This is a big step forward for allowing journalists to make un/less traceable first contact with sources without compromising either party.
In the (basic) infosec for journalists class that I teach, this has always been a sticking point and now there is a (not perfect but really great) solution. 👍