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


But privacy doesn’t depend on a payment per se, but entirely on the type of payment method offered (which we don’t know yet, as I already stated in my original comment).
Coming back to e.g. Threema: You can buy a working Threema license key using completely anonymous payment, e.g. bitcoin, or even by cash.
Having the option to pay instead of providing the phone number has the potential to be the much more privacy friendly option, if it is done right…
Seems a bit difficult, I’m not particularly interested in going through all the hoops that come with trying to own cryptocurrency anonymously, and actual cash payments don’t seem practical considering that the Signal organisation is US-based (I don’t live in America; I’d absolutely try my luck with sending a letter with a 5€ note to e.g. Switzerland).
And it’s not really about the price, I’d happily donate 3.50, but not directly tied to my messenger account.
It isn’t tied to the account, the developers in the forums say so. It uses a zero-knowledge proof so the account and the payment aren’t linked.
That’s neat if true, thanks.