[Q] External SD issue on Z Ultra GPE with Android 5.0 (Lollipop) topic

I installed Android Lollipop on my Z Ultra GPE (Stock version via OTA) and tried to use External SD card by using 3rd-party apps which say "Lollipop supported" (e.g., ES file manager, Root explorer, Solid explorer, etc.)
Issue is, I cannot grant the permission for accessing External SD card to these 3rd-party apps - when I try to do it, the windows for choosing Internal/External storage only shows the device's Internal storage, not its External SD card.

Could anyone help me on this issue?
I suggest that if it is intended by Google, all GPE devices will not be able to access to External SD card even in Android Lollipop.