[FYT Android Head Units] mastrv:
I was trying this out on my head unit. Those documentsui apk also force close on mine.

I looked at the logcat and there's a lot there. I saw a few issues about permissions for external storage but the app isn't requesting any permissions in the app settings. This looks like the relevant exception:

09-20 09:07:05.427 I/ActivityManager(3973): START u0 {act=android.intent.action.CREATE_DOCUMENT cat=[android.intent.category.OPENABLE] typ=application/x-poweramp-settings cmp=com.android.documentsui/.picker.PickActivity (has extras)} from uid 10108, pid 5211
09-20 09:07:05.441 I/ActivityManager(3973): ->startActivity for ActivityRecord{adc44cb u0 com.android.documentsui/.picker.PickActivity t3} result:0
09-20 09:07:05.442 D/performance(3973): getRecentTaskThumbnail----->Intent { act=android.intent.action.CREATE_DOCUMENT cat=[android.intent.category.OPENABLE] typ=application/x-poweramp-settings cmp=com.android.documentsui/.picker.PickActivity (has extras) }
09-20 09:07:05.472 I/ActivityManager(3973): Start proc 7168:com.android.documentsui/u0a186 for activity com.android.documentsui/.picker.PickActivity
...
09-20 09:07:05.546 E/BufferQueueProducer(3515): [com.maxmpz.audioplayer/com.maxmpz.widget.base.AlertDialogActivity#0] disconnect: not connected (req=1)
09-20 09:07:05.546 W/libEGL (5211): EGLNativeWindowType 0xbe8fd008 disconnect failed
09-20 09:07:05.546 D/OpenGLRenderer(5211): endAllActiveAnimators on 0xb9f75c00 (RippleDrawable) with handle 0xbef7e160
09-20 09:07:05.595 W/ActivityManager(3973): Permission Denial: opening provider com.android.externalstorage.ExternalStorageProvider from ProcessRecord{166c731 7168:com.android.documentsui/u0a186} (pid=7168, uid=10186) requires that you obtain access using ACTION_OPEN_DOCUMENT or related APIs
09-20 09:07:05.604 E/AndroidRuntime(7168): FATAL EXCEPTION: AsyncTask #1
09-20 09:07:05.604 E/AndroidRuntime(7168): Process: com.android.documentsui, PID: 7168
09-20 09:07:05.604 E/AndroidRuntime(7168): java.lang.RuntimeException: An error occurred while executing doInBackground()
09-20 09:07:05.604 E/AndroidRuntime(7168): at android.os.AsyncTask$3.done(AsyncTask.java:353)
09-20 09:07:05.604 E/AndroidRuntime(7168): at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:383)
09-20 09:07:05.604 E/AndroidRuntime(7168): at java.util.concurrent.FutureTask.setException(FutureTask.java:252)
09-20 09:07:05.604 E/AndroidRuntime(7168): at java.util.concurrent.FutureTask.run(FutureTask.java:271)
09-20 09:07:05.604 E/AndroidRuntime(7168): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1162)
09-20 09:07:05.604 E/AndroidRuntime(7168): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:636)
09-20 09:07:05.604 E/AndroidRuntime(7168): at java.lang.Thread.run(Thread.java:764)
09-20 09:07:05.604 E/AndroidRuntime(7168): Caused by: java.lang.SecurityException: Permission Denial: opening provider com.android.externalstorage.ExternalStorageProvider from ProcessRecord{166c731 7168:com.android.documentsui/u0a186} (pid=7168, uid=10186) requires that you obtain access using ACTION_OPEN_DOCUMENT or related APIs
09-20 09:07:05.604 E/AndroidRuntime(7168): at android.os.Parcel.readException(Parcel.java:2004)
09-20 09:07:05.604 E/AndroidRuntime(7168): at android.os.Parcel.readException(Parcel.java:1950)
09-20 09:07:05.604 E/AndroidRuntime(7168): at android.content.IContentService$Stub$Proxy.registerContentObserver(IContentService.java:768)
09-20 09:07:05.604 E/AndroidRuntime(7168): at android.content.ContentResolver.registerContentObserver(ContentResolver.java:1924)
09-20 09:07:05.604 E/AndroidRuntime(7168): at android.content.ContentResolver.registerContentObserver(ContentResolver.java:1913)
09-20 09:07:05.604 E/AndroidRuntime(7168): at com.android.documentsui.roots.ProvidersCache.loadRootsForAuthority(ProvidersCache.java:256)
09-20 09:07:05.604 E/AndroidRuntime(7168): at com.android.documentsui.roots.ProvidersCache$UpdateTask.handleDocumentsProvider(ProvidersCache.java:477)
09-20 09:07:05.604 E/AndroidRuntime(7168): at com.android.documentsui.roots.ProvidersCache$UpdateTask.doInBackground(ProvidersCache.java:446)
09-20 09:07:05.604 E/AndroidRuntime(7168): at com.android.documentsui.roots.ProvidersCache$UpdateTask.doInBackground(ProvidersCache.java:434)
09-20 09:07:05.604 E/AndroidRuntime(7168): at android.os.AsyncTask$2.call(AsyncTask.java:333)
09-20 09:07:05.604 E/AndroidRuntime(7168): at java.util.concurrent.FutureTask.run(FutureTask.java:266)
09-20 09:07:05.604 E/AndroidRuntime(7168): ... 3 more
09-20 09:07:05.605 D/HprofFactory(7168): Create HprofDebugEx
09-20 09:07:05.611 W/ActivityManager(3973): Force finishing activity com.android.documentsui/.picker.PickActivity
09-20 09:07:05.611 I/System.out(4232): com.android.launcher3
09-20 09:07:05.612 I/System.out(4232): ch.deletescape.lawnchair.plah
09-20 09:07:05.612 I/System.out(4232): com.android.settings
09-20 09:07:05.613 E/timer (4232): appName Files
09-20 09:07:05.615 D/PowerController.AppState(3973): - reportAppStateEventInfo() E -
09-20 09:07:05.615 D/PowerController.RecogA(3973): handleMessage(MSG_REPORT_EVENT)
09-20 09:07:05.615 I/System.out(4232): com.android.launcher3
09-20 09:07:05.615 I/System.out(4232): ch.deletescape.lawnchair.plah
09-20 09:07:05.615 I/System.out(4232): com.android.settings
09-20 09:07:05.616 E/demo (4232): mViews size = 1
09-20 09:07:05.616 W/ActivityManager(3973): Force finishing activity com.maxmpz.audioplayer/com.maxmpz.widget.base.AlertDialogActivity

I think this may be something that PowerAmp may/should be able to address. This exception says:

java.lang.SecurityException: Permission Denial: opening provider com.android.externalstorage.ExternalStorageProvider from ProcessRecord{166c731 7168:com.android.documentsui/u0a186} (pid=7168, uid=10186) requires that you obtain access using ACTION_OPEN_DOCUMENT or related APIs

Perhaps you should post this on the Poweramp forum and see what comes of it.

I also read something interesting here: https://source.android.com/docs/core/architecture/modular-system/documentsui

Says that starting in Android 12, file browsing through DocumentsUI is disabled. I think that means that when/if Poweramp is to support Android 12, they'll need to modify the code they use for selecting/creating an export file will need to be modified.