Tinfoil hat answer: The fact that he is alive and did not even catch a bullet shows that it was staged. You want to tell me a guy with a shotgun runs towards American police officers and nobody even shoots him? Sounds fake. They must have had orders to not actually shoot him, stage a small gunfight and then just arrest him. The guy probably got a good paycheck for his upcoming prison time.
They did not ban encrypted communications in general. They just banned the use of Signal for official purposes, because it is not fit for the job.
The article talks about how there were a multitude of cyberattacks and phishing attempts on EU officials’ smartphones and Signal accounts. With Signal, you have full control over the whole Account if you control the device.
The EU has their own encrypted communication tools with security and accounts managed centrally by the IT department.
As someone who uses GrapheneOS with sandboxed GooglePlay on his only smartphone (with daily usage for years at this point): I don’t know what kind of adjustment you are referring to. I never had to adjust to anything, because I never encountered anything that GrapheneOS couldn’t do that stock Android could. Follow the installation process and after that the phone behaves like a regular phone, except you have way more options regarding security and privacy.
Is your friend trying to use GrapheneOS without any Google services maybe?
How did they arrest him then?