If it's free and open source and it's also software, it can be discussed here. Subcommunity of Technology.
This community's icon was made by Aaron Schneider, under the CC-BY-NC-SA 4.0 license.
Sign-up still requires a phone number.. -.-"
Checkout Matrix/Element ~~or Session~~,
there you can actually enjoy privacy by signing-up without a phone number/email:
Edit: Due to Session's company residing in Australia,
which appareantly has bad privacy laws,
i don't feel comfortable with recommending it anymore
Ah yes, Signal, known anti-privacy company
Sign-up still requires a phone number… -.-"
Thanks for the warning -- that was my first question. It is my top reason (among many other reasons) for avoiding Signal.
Checkout Matrix/Element or Session,
All 3 of the sites you linked are Cloudflare sites (thus antithetical to privacy). Yes, I know you can use some of that tech without touching CF, but when they run CF websites it reveals hypocrisy & not understanding the goals of their audience.