Chinese Warnings on iPhones Tap Deep Strain of Security Concerns

China has discouraged the use of foreign-made electronic devices by government officials for a decade. It has told agencies and state-owned companies to replace American computer servers and other devices with domestic ones. And officials frequently show off to Americans their phones made by Huawei, China’s cellphone giant.

Now, some employees of government agencies said they have received directives not to use Apple iPhones for work….