ZED-M on USB2.0: IMU works but no video device

[RBJin]

Preliminary Checks

• This issue is not a duplicate. Before opening a new issue, please search existing issues.
• This issue is not a question, feature request, or anything other than a bug report directly related to this project.

Description

• Does ZED-M support USB2.0 video mode?
• Or is the "USB2.0 supported in VGA mode" note in the README only valid for ZED / ZED2 / ZED2i?

Steps to Reproduce

1. Connect a ZED-Mini camera to a development board that only has USB2.0 ports.
2. Boot Ubuntu 20.04 (minimal rootfs), kernel 4.19.232.
3. Build and install zed-open-capture from master branch (v0.6.0).
4. cd udev && bash install_udev_rule.sh
5. ./zed_open_capture_control_example
6. ./zed_open_capture_sensors_example

Expected Result

According to the README, USB2.0 should be supported in VGA mode.
I expected to see a /dev/videoX device for the camera.

Actual Result

• lsusb shows only HID device (2b03:f681 ZED-M Hid Device).
• No new /dev/videoX appears for the camera.
• v4l2-ctl --list-devices only lists platform rkisp devices.
• The zed_open_capture_control_example prints:

[sl_oc::video::VideoCapture] INFO: ZED Open Capture - Camera module - Version: 0.6.0
[sl_oc::video::VideoCapture] INFO: Camera resolution: 1344x376@15Hz
[sl_oc::video::VideoCapture] INFO: Trying to open the device '/dev/video0'
[sl_oc::video::VideoCapture] WARNING:  not a modalias 2
[sl_oc::video::VideoCapture] WARNING: The device '/dev/video0' is not a Stereolabs camera
[sl_oc::video::VideoCapture] INFO: Trying to open the device '/dev/video1'
[sl_oc::video::VideoCapture] WARNING:  not a modalias 2
[sl_oc::video::VideoCapture] WARNING: The device '/dev/video1' is not a Stereolabs camera
[sl_oc::video::VideoCapture] INFO: Trying to open the device '/dev/video2'
[sl_oc::video::VideoCapture] WARNING:  not a modalias 2
[sl_oc::video::VideoCapture] WARNING: The device '/dev/video2' is not a Stereolabs camera
[sl_oc::video::VideoCapture] INFO: Trying to open the device '/dev/video3'
[sl_oc::video::VideoCapture] WARNING:  not a modalias 2
[sl_oc::video::VideoCapture] WARNING: The device '/dev/video3' is not a Stereolabs camera
[sl_oc::video::VideoCapture] INFO: Trying to open the device '/dev/video4'
[sl_oc::video::VideoCapture] WARNING:  not a modalias 2
[sl_oc::video::VideoCapture] WARNING: The device '/dev/video4' is not a Stereolabs camera
[sl_oc::video::VideoCapture] INFO: Trying to open the device '/dev/video5'
[sl_oc::video::VideoCapture] WARNING:  not a modalias 2
[sl_oc::video::VideoCapture] WARNING: The device '/dev/video5' is not a Stereolabs camera
[sl_oc::video::VideoCapture] INFO: Trying to open the device '/dev/video6'
[sl_oc::video::VideoCapture] WARNING:  not a modalias 2
...
Cannot open camera video capture

ZED Camera model

ZED Mini

Environment

- Camera model: ZED-M
- Connection: USB2.0 only (board has no USB3)
- Board: LubanCat (Rockchip platform)
- OS: Ubuntu 20.04 minimal (custom build)
- Kernel: 4.19.232
- zed-open-capture version: v0.6.0 (master branch)

Anything else?