Interesting that a recent KA crew in Shanghai on a turnaround were met by police security who asked for all their phones. They then inserted a device to the phone, which is known to download a tracking and reporting software into the phone.
This device has been reported recently by private citizens and by foreign journalists, (NYT passim), particularly those visiting Uighur areas. It is believed this is the first time that it has been installed on a foreign aircrew’s phone
One cabin crew member initially refused to allow the software installation but was threatened with being taken off the aircraft, so relented.
So if you must take a phone on a mainland turnaround, take a burner 😳