Presently, JUCE #undefs JUCE_USE_CAMERA when not building for macOS or Windows.
#if ! (JUCE_MAC || JUCE_WINDOWS)
#undef JUCE_USE_CAMERA
#endif
Thing is, the framework supports this feature on both on macOS, iOS, Windows, and Android if you look at the implementation file:
#if JUCE_MAC || JUCE_IOS
#include "../native/juce_mac_CameraDevice.h"
#elif JUCE_WINDOWS
#include "../native/juce_win32_CameraDevice.h"
#elif JUCE_ANDROID
#include "../native/juce_android_CameraDevice.h"
#endif
Looks like it should just be #undeffing on Linux?
#if JUCE_LINUX || JUCE_BSD
#undef JUCE_USE_CAMERA
#endif
