It’s the other way around. The Alexa device is attempting to connect to the RTSP stream and performing a DESCRIBE requests as part of the RTSP protocol. It’s the RTSP server (v4l2rtspserver) that is giving the 404 error in response to the DESCRIBE request.
This would typically mean the RTSP URL is wrong, but it could also mean the RTSP server did not accept how we (Monocle Gateway) formed the request.
Is there any way you can temporarily host this stream and allow us to connect to it from here across the Internet. We can perform some additional tests. Is so, you can PM me the connection details.
Thanks, Robert