No audio playback in the Android app on Boox e-readers (Opus codec disabled in firmware)

Read-aloud playback in the Storyteller Android app produces no sound at all on my Boox e-reader. The book opens, the text highlights, but nothing comes out of the speaker or over Bluetooth. Other apps play audio fine on the same device.

Resolution: Boox ships firmware with the Opus audio codec deliberately removed from the codec list, so any Opus-encoded audio silently fails to decode. You can confirm it on-device: adb shell 'grep -n -i -B2 -A1 opus /vendor/etc/media_codecs_google_c2_audio.xml' shows the c2.android.opus.decoder and c2.android.opus.encoder entries commented out with <!-- Disabled: Opus decoder -->. The shared libraries are still present (libcodec2_soft_opusdec.so, libcodec2_soft_opusenc.so, libopus.so under /apex/com.android.media.swcodec/lib64/) but the app cannot reach them because they are no longer advertised in MediaCodecList, and /apex is not accessible without root. There is no app-side setting that fixes this; the only real workaround today is to use audiobook source files in a codec the device does still support (AAC/M4B or MP3) rather than Opus. A bundled Opus decoder via the NDK is the only path to fixing it without Boox's cooperation.