Hi, I was hoping that too, but unfortunately it doesn’t support 24-bit at all and peaks out at 16/48 from info on amazon’s own help pages for digital output to an amp etc:
Supported Digital Connection Formats
Digital Audio Inputs (optical TOSLINK and coaxial RCA) - Uncompressed PCM audio (16bit/44.1, 48, 88.2 or 96kHz)
Digital Audio Output (optical TOSLINK and coaxial RCA) - 16bit/48kHz Uncompressed PCM stereo
It’s interesting (or disappointing) that the Alexa app doesn’t show or tell you the quality when streaming to the Echo Link, unlike the Amazon Music Apps.
It’s also telling that they have only just listed their Echo Studio speaker under supported kit on their splash page - no sign of the Link.
I think what’s becoming clear is that their own Amazon Music apps aren’t up to the delivery of their UHD service - hopefully they’ll address that as this, and other forums, are clamouring for improvement.