After the Tchap project based on Matrix, the French Prime Minister asks anyone in the gouvernement to use Olvid, the only app validated by the ANSSI, with metadata encryption and no centralised architecture nor contacts discovery. But only the front-ends are open source, not the back-end.
To start Europe should have secure phones made in EU.
Doesn’t switching instant messaging services count as a start? Switching hardware is far harder than switching software.
Also, local messaging systems also determine where your traffic goes and who controls that data. If you have a french messaging service with data centers in france routing traffic between people in France, you are in a far better shape.