Technological solutions only go so far when offline restrictions can be imposed. It's entirely likely that once Signal figures out username based registration & sees some traction in, Governments will just ban it.
> In March 2017, Signal was approved by the Sergeant at Arms of the U.S. Senate for use by senators and their staff. https://www.zdnet.com/article/in-encryption-push-senate-appr...
> The European Commission has told its staff to start using Signal, an end-to-end-encrypted messaging app, in a push to increase the security of its communications. https://www.politico.eu/article/eu-commission-to-staff-switc...
https://www.politico.com/story/2019/06/27/trump-officials-we...
https://www.eff.org/deeplinks/2020/10/urgent-earn-it-act-int...
http://cyberlaw.stanford.edu/blog/2020/06/there%E2%80%99s-no...
The US and cryptography have never really gotten along.
take for example matrix or discord. these services because of their non phone nature, it is very difficult for police to track down dissent. encryption is a fancy word when you are the only one using it.
i remember actively avoiding using tor back a decade ago because while it could be used to securely communicate online, i would have been the sore thumb.
mass adoption of encryption of all forms in all communications without leaving afk trails is the only way to keep internet safe from governmental control.