There is trial going on is France right now against 7 people accused of "association of terrorist criminals”.
They haven’t done anything but they had a “clandestine behavior” (aka they used signal and proton to communicate with each other) which is enough apparently to indict them.
“All members contacted adopted a clandestine behaviour, with increased security of means of communication (encrypted applications, Tails operating system, TOR protocol enabling anonymous browsing on the Internet and public wifi)”. General Directorate for Internal Security
“All members of this group were particularly suspicious, only communicating with each other using encrypted applications, in particular Signal, and encrypting their computers and devices […]." The Investigating Judge