Signal has started rolling out Signal Login, an optional registration method that allows users to create a Signal account without providing a phone number. The feature will be rolled out first on Android and will come to iOS later.
As we previously reported, Signal Login is not a free alternative registration method. Signal requires users who choose to register without a phone number to make a one-time payment. The price at launch is $2.99 / € 3.49, although this may vary by region and currency.
Session seems pretty good for this! Not sure if forward secrecy is fully implemented yet but it’s in the works. User interface seems really easy so far.
Not sure about the stability of the maintainers but the FOSS community has been actively supporting it.