Poweramp won't open under GrapheneOS on Pixel 5a

[NobodyInParticular]

OS: GrapheneOS (Android 11)

Phone: Pixel 5a

Installed Poweramp, gave it access to Files & Media, network and sensors. Have Google Play Store running in sandbox, but with no permissions. When I try to open Poweramp, it doesn't open.

What else must I do to run it?

[NobodyInParticular]

Update. I found the following information in the Poweramp FAQ: 

Quote

Please ensure, that following system app exists and is not disabled on your device (you may need to select some option to show all apps / system apps):

• Files (com.google.android.documentsui)
  

You can also restore that system dialog functionality by installing Files by Google app from Play (https://play.google.com/store/apps/details?id=com.google.android.apps.nbu.files&hl=en)

Package Disabler (and similar apps): If you're using Package Disabler or similar app, ensure critical system components (which disabler apps may mistakenly marks as "bloatware") are NOT disabled:

• External Storage (com.android.externalstorage)
• Files (com.google.android.documentsui)
• Media Storage (com.android.providers.media)
• Permission controller (com.google android.permissioncontroller)

All of these apps exist and are enabled except com.google android.permissioncontroller, which GrapheneOS replaces with com.android.permissioncontroller. When started, Poweramp sometimes displays its UI for an instant, then immediately closes. 

Has anyone else running GrapheneOS got Poweramp running?

[NobodyInParticular]

I installed Leopard7's Music Player and got it running without a hitch after granting it access to my media files. Then, mysteriously, Poweramp started working without my changing anything else. I uninstalled Music Player and Poweramp still works fine.