Andrew Fafen, on his blog:

The HomePod has great sound quality, but right now it’s limited to playing audio from Apple Music or AirPlay clients like the iPhone or iPad. But what if you want to play audio from other sources? Ideally the HomePod would have a line-in port, show up as a Bluetooth speaker, and support other streaming services like Spotify. But Apple decided not to include a line-in port, hasn’t yet implemented Bluetooth speaker support in the OS, and hasn’t yet natively supported other streaming services.

Hopefully Apple will eventually address these shortcomings on the HomePod itself, but for now I’ve come up with my own solution. I’ve taken a Raspberry Pi Zero W […] and written software that takes audio input from line-in or Bluetooth and outputs it wirelessly to the HomePod via Airplay. I call it BabelPod since it acts as a universal translator between audio devices.

I love solutions such as this one, because while they shouldn’t be necessary — the HomePod should have Bluetooth audio streaming support and a line-in port included — they do solve the problems of some people.