I am also doing same process, but I am not able to flash the bootloader.
Once firmware become secure, I can’t connect it through MAVProxy/Mission Planeer/ QGC.
[45820.211631] usb 1-2: Product: CubeOrange±Secure-BL-v10
[45820.211633] usb 1-2: Manufacturer: CubePilot
[45820.212309] usb 1-2: SerialNumber: 2F0052001851313334373032
[45820.221937] cdc_acm 1-2:1.0: ttyACM4: USB ACM device
eshma@Myubuntu:~/coptor4.3.5/ardupilot-Copter-4.3.5$ mavproxy.py --master=/dev/ttyACM4
Connect /dev/ttyACM4 source_system=255
Log Directory:
Telemetry log: mav.tlog
Waiting for heartbeat from /dev/ttyACM4
MAV>
Pl
MAV> link 1 down
Can you please let me how you flashed bootloader?