Everyone has own experience.
I'm using this for external SD:
Code:
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This "iGO_Maps" must have subfolder "content" which must have it's subfolders (building, dem, map, phoneme, poi and speedcam) depending on which content you put there, but no other content.
On systems from Android 4.xx to 10.xx, and never had any problem.
On Android 4.xx, "8489-1917" is changed to "sdcard1"

If content is in internal memory then "8489-1917" is changed to "emulated/0" (on newer androids) and to "sdcard0" on Android 4.xx.

This always worked for me with all NG versions and also with "classic" Primo.
Also, you must be careful which content is in separate folder.

Problem with "black screen" was always related to specific app version on specific Android version, and sometimes only on specific device.