Session comes with its own anonymity network...you sometimes need a VPN to access it, but still.
And even though there's no quantum encryption on it yet. Whoever would try to use a quantum computer to break in would still need to use it for quite awhile on hundreds of different servers each processing thousands of different people's traffic at any time.
Threema is decent, too. Crypto is comparable, and allows signups without email or phone number.
It's a paid app, though, but anonymous purchase options are available.