Friends who ask questions, you can go to the police station or criminal police team where your friend was arrested first. It's been two months now, and people and cases must have been handed over to the preliminary examination. You ask which pre-trial department they handed over, that is, which pre-trial examiner in several pre-trial rooms or groups. Don't worry, the police at the police station or the criminal police team will definitely tell you. As you can see from the question you mentioned, you must make sure that your friend was captured by the public security bureau, not lost. If you really don't know which department took it, you can report the loss of population to the police station where your friend's household registration is located, and ask the police at the police station to help you find out where your friend is now. The public security network can inquire. You don't need to read any legal provisions, can you understand them? Notifying family members is a procedure and has no practical significance. There is no notice now. What I told you is practical, with many rules, not 100%. Do as I say and make sure you know where it is.
Finally, I wish your friend good luck.