QFileDialog::getOpenFileName always returns empty string on Android

I have working code (on Windows & Linux) that I compiled for Android: https://github.com/MayaPosch/NymphCast/tree/master/player/NymphCastPlayer

Everything works just like on Linux and Windows, except that when I try to open a local file, I cannot get a file path back from getOpenFileName(). When this function is called, I do get the native Android (Android 8) file picker dialogue for local files, and I can select anything.

Yet the return value is always an empty string. This happens with Qt 5.13.2 and 5.14.2, and with a somewhat older SDK & NDK (20.x), as well as the (as of writing) latest SDK & NDK (21).

I have made sure that the AndroidManifest has the 'android.permission.WRITE_EXTERNAL_STORAGE' and 'android.permission.READ_EXTERNAL_STORAGE' permissions.

I'm running the APK on a Xiaomi Mi 5, with MIUI 10.2 (Android 8.0).

Since QFileDialog::getOpenFileName() clearly calls an Intent, it would make sense that it would also have provisions to get the results from said Intent. If this has been implemented, it does not appear to be working.