

If you’re trying to daily drive it, I’d recommend strongly against it. It’ll be an absolutely miserable experience for you, and probably will be quite slow even if you’re using it as a wall display.
That being said, this xda post seems to still have a live file. Hopefully it’s what you need
If this is part of your threat model and you are using lineage on a device that supports avb_custom_key then you can sign it yourself before flashing
Interesting behavior. Turn-by-turn uses a different audio channel than music, so it would make sense for that to work while music doesn’t. Music only coming from the center speaker is weird. I’m assuming you’re not playing surround encoded media. Have you tried resetting the Android Auto app, and bar that Google Play Services itself? (Note that resetting Google Play services will reset any connected wear os devices)
Is Power Amp installed from Google Play or side loaded? Android Auto will inexplicably refuse to launch side loaded apps half of the time. If it is launching but no audio is coming out, this isn’t the solution for you
To get around that I download my app (in my case, CoMaps) via Obtainium + Shizuku with the option “Set Google Play as the installation source”
Since Poweramp isn’t FOSS, you’ll have to download their provided apk & move it to /data/local/tmp with adb
Then you can run pm install -i "com.android.vending" /data/local/tmp/Poweramp-build-999-uni.apk
This will overwrite the installed app’s installation source with Google Play and let Android Auto work with it
In America, we’re lucky if our bank supports 2fa, let alone require an app for it