If the Denon statement you quoted is from the link below, then that just refers to the Heos app and what I was able to do when I bought my Heos Link HS2 almost four years ago. Do you have a link for where you got the seemingly more recently dated info?Just gotta figure out how that coorelates with the Denon HEOS statement of the contrary. There has got to be someway that someone can measure exactly whats being streamed to the AVR through the WiFi connection. On the phone, I'm sure "there's an app for that?. But how to do it for the AVR?
https://support-uk.denon.com/app/an...aying-amazon-ultra-hd-music-on-my-heos-system
The only change I recall (just after I sold my HS2 and bought the WiiM Mini) was the ability to access your own user playlists. I can’t see anything that suggests they upgraded their Heos skill to support lossless playback via Alexa or AlexaCast from the Amazon Music app - indeed, it would have needed Amazon to update Alexa‘s handling of skill audio and I haven’t seen any sign of that either.
I’m sticking to my guns that the WiiM devices are the only devices that will support bit perfect casting up to 24/192 from the Amazon Music app and that the best you’ll get for other devices is probably just MP3, with maybe a slim chance that ChromeCast might offer HD even though Amazon say it doesn’t support lossless playback with that.
I guess you might be able to use some sort of network analysis (maybe via your router) to see how much traffic is sent to your AVR when casting from the Amazon Music app and from that infer the bitrates being played