Could it be that the processor sends data from the camera/microphone to the Qualcomm/Mediatek servers, bypassing the system? Is it possible to find out about this by checking the traffic leaving the device? Are there any studies that have done this? If this happens, then even GrapheneOS becomes mostly meaningless.
Yes, its possible to check. Data has to be sent through some connection, and we are able to monitor all traffic going through connections we control. Its not happening on wifi and not on 4G/etc. So unless there is some other connection that is not a real issue.
It would be interesting to see research on this topic :)