How to disable automatic screen mirroring when connecting iPhone to monitor via USB C cable

Title.

At work the only charging option is through the monitor USB C cables.

There is no device that shows up on Screen Mirroring yet I can clearly see my iPhone is mirrored on the display when the cable is plugged in!!!

This is a massive privacy flaw!

[Edited by Moderator]

Original Title: How to disable automatic screen mirror when connecting iPhone to external monitor via USB C cable