I am the developer of "AirMusic" (aka AirAudio, https://play.google.com/store/apps/details?id=app.airmusic.trial).
This app allows Android-users to stream any app's audio to almost all audio-protocols.
Since Android 10+, AirMusic can record the submix of other apps without having to "root" the device.
Sadly it seems like Poweramp explicitly disallows that their app gets recorded by 3rd-party-apps or something else is causing this issue.
Can you please have a look at this page? https://developer.android.com/guide/topics/media/playback-capture#allowing_playback_capture
Maybe you can give me some feedback about the reasons or with some luck this is something you could change in near future?
Several users have contacted me because they cannot stream your music and I am a paid user of Poweramp since 2012 too.
Would be great if we can get this working so users can stream their beloved Poweramp-player to their remote speaker :)
Best regards from Germany,