Hi
Seems that although APM supports ROI mode (at least in ArduCopter, I did not test with other vehicles) it is not declared nor in APMFirmwarePlugin::isCapable neither in ArduCopterFirmwarePlugin
Is It intentional ?
ArduPilot supports the old deprecated MAV_ROI mavlink commands. It does not support the new MAV_CMD_DO_SET_ROI_* commands which is what QGC supports for multiple years now.
looking at ArduPilot code - https://github.com/ArduPilot/ardupilot/blob/master/libraries/GCS_MAVLink/GCS_Common.cpp#L3800
Seems that MAV_CMD_DO_SET_ROI_LOCATION and MAV_CMD_DO_SET_ROI are both handled
MAV_CMD_DO_SET_ROI_NONE is missing which prevents you from being able to cancel an ROI. Which prevents the Fly view from being able to set/cancel an ROI which is what this isCapable is for. Also unrelated to this specific case but MAV_CMD_DO_SET_ROI_WPNEXT_OFFSET is needed to make Structure Scan work with ARDUPILOT.