Offboard Control over USB port

I would like to do the offboard control using a USB port instead of Telem2. However, it seems like the mavlink messages aren’t streamed out on /dev/ttyACM0 by default. I have to open QGC and do ‘mavlink start -d /dev/ttyACM0’. Is there a way to write a code on the companion computer to have messages streamed by default? I know the code must exist somewhere in QGC but couldn’t find the right file to look for.
Best regards,

Mine is on by default.
nsh> mavlink status

instance #0:
MAVLink version: 1
transport protocol: serial (/dev/ttyS5 @115200)

instance #1:
type: USB CDC
MAVLink version: 2
transport protocol: serial (/dev/ttyACM0 @2000000)

I’m running a Pixhawk 6c with a nightly build from source (10/19/2022)
Screen Shot 2022-10-21 at 8.50.39 AM

I use docker to communicate with /dev/ttyUSB0