Running multiple drones in gazebo-classic headless mode

Hello! I’m a newbie to PX4 and I was trying to run multiple drones in gazebo-classic. The HEADLESS=1 environment variable seems to work only when there is one drone involved, and it seems just plainly ignored when running I also tried to comment out the call to gzclient at the end of the script but that seems to make communication with MAVSDK or QGroundControl impossible. Is there something I’m missing?