Some comments that I have recently found. For some reasons (I am not sure 100%), if you used v0.96 with flight controller via Mavlink and try to use mavros, you will not be able to get any messages from orientation topic, which means no feedback from there. I am not sure about the reason, but the current thoughts/findings (I might be wrong) that the firmware was not supporting to give orientation readings via mavlink that’s what I see from mavlink_strom32.xml file from the firmware and because of the firmware is closed(Designing a standard, open source gimbal controller - #2 by hamishwillee), you will not be able to edit the firmware and change the xml file unfortunately. Also, I am not sure if it is the case for the newer firmware versions or not.
However, if you want to get orientation within ROS, you can use this: GitHub - mcgill-robotics/ros-storm32-gimbal: 📸 STorM32 gimbal controller ROS driver I have tested that package, it worked good for control and returning the orientation relatively to the initialization pose!