Alexa Media Player: Unable to play local audio files (“Direct Music Streaming isn’t supported”)

Hi everyone,
I’m trying to play a short local sound file on my Echo (1st Gen / Echo Plus) via Home Assistant — basically an “Iron Man startup sound” that should play before my ESPHome-controlled lights slowly fade in.

The file is stored in the /www directory and is accessible through Nabu Casa, for example:
https://…ui.nabu.casa/local/Ironman_Start.wav
It plays perfectly fine in the browser.

However, when I call:

service: media_player.play_media
data:
  entity_id: media_player.xxx_echo
  media_content_id: "https://.../Ironman_Start.wav"
  media_content_type: "music"

Alexa responds with:

“Direct Music Streaming isn’t supported.”

If I switch to media_content_type: sound, there’s no error — but also no sound.

TTS messages work perfectly fine, as do Amazon’s built-in sound effects like bell_02.

From what I’ve read, Amazon seems to block direct playback of custom URLs.
I’m therefore looking for a workable solution or alternative approach — for example, Bluetooth output from Home Assistant to the Echo, a Spotify workaround, an external Wi-Fi speaker, or maybe something completely different.

Has anyone here successfully managed to play custom local audio files on an Echo device from Home Assistant — or found a creative way to trigger short sound effects through Alexa?

Thanks in advance for any ideas or workarounds!

The issues above are answered in my post in the other thread you posted in.

You must use Alexa’s Notify platform, and the .wav file format is not acceptable under Alexa’s requirements.