Android As USB Music Streamer

There seems to be an opportunity to make streamers from old Android Phones.

But the software seems to lack.

The phone has so many opportunities:
  • USB out
  • Big screen with touch
  • Autodimmable screen
  • Power for EQ and Room Correction
  • Battery for playback time & USB for auto charge
  • Fast SSD with typical 128 GB, some even an SD card.
  • LDAC/APTX Bluetooth receiver
  • USB hub could connect to LAN and split into separate power and data
  • USB Hub could also add extra storage or LAN to the server.

People happily happy 800 USD for streamers with this functionality. We could do all the above with a basic 70 EUR/USD hub and software.

Environment - these phones collect dust, but even my 2019 phone has all the above. All it needs is an enclosure and software to work as an endpoint.
Spotify has this almost set correctly, but ideally, we wanted to set this up as a Roon endpoint or with 4Stream / Wiim software as a dedicated software on top of some stock Android installation. It should also make sure the input and output is bit-perfect.

Another opportunity would be to sell enclosures and a USB/power/coaxial/LAN hub to connect for all features to work perfectly.

I looked at Volumio, Roon, Plex, Kodi, and Moode and I don't see anyone being able to support it. It could also be a simple App in the app store, but I think a rooted clean install with more software control, would function better and remove all unnecessary components. I hope there would be some more ideas or support for such a software developed.

Thoughts?
 
From the HW POV an android phone is a perfect streamer. But from the SW POV:

  • Android linux kernels tend to be extremely outdated.
  • Until recently they had only old UAC1 drivers. While mainline linux kernel supports countless USB DACs out of the box, android kernels by google did not have the full alsa usb drivers stack. That's why apps like USB player had to program UAC2 support using user-space libusb or google android usb hooks.
  • If you replace the old android kernel with latest mainline, many hardware components will stop working as android ARM SoC vendors typically do not upstream their drivers to mainline. Only some do, and even those take years (e.g. Rockchip).
  • A linux app (like volumio) cannot be just turned simply into an android app. It's a completely different user-space system.

Yes there are streamers using android, but the vendors put a lot of effort into building a custom kernel which supports both their chosen SoC features (typically forward-ported from android kernel) and new mainline kernel features (like alsa usb drivers with latest HW quirks etc.). Then they wrote a custom android playback app, for their HW.

IMO it's doable, but quite a major task.