Proton suffers from the Lavabit problem but worse, it pretends to offer security and freedom when it does neither and acts as a tool of foreign governments to abuse individuals. Use your own GPG keys and better clients, preferably with self-hosting in Iceland or Sweden.
For truly sensitive communication, it’s better to use Signal: https://soatok.blog/2024/11/15/what-to-use-instead-of-pgp/
You're a fool if you believe handing over metadata like your personal phone number so you can be tracked is an improvement. That's not email and not a replacement for GPG, something that actually works properly. Session is a superior app for text replacement. I think you need to find new blogs that don't offer crap advice.
They resisted this change for years, but eventually gave in and fixed it. You no longer need to hand out your phone number.
What kind of threat model do you operate under where Signal Technology Foundation knowing (one of) your phone numbers is a large risk?
The fact that signal knows my phone number doesn't bother me.
The fact that anyone who knows my phone number can know that I use signal does bother me.
Session started as a fork of the Signal client/server to use identifiers that are not phone numbers (perfectly sensible) but having deviated from the known primitives of the Signal protocol and omitting PFS gives me pause.