And this is from Yamaha support about Amazon Music: I have the A6A.
Thank you for contacting Yamaha Customer Support. Amazon HD music is supported on this receiver. However, none of our products can stream Amazon Ultra HD music. You may wish to use another device, like a laptop, to stream the Ultra HD audio and connect it to the receiver with an analog connection instead. Regarding your MQA support questions, I do not have any information regarding what will be supported in future firmware versions. I hope you find this information helpful. Please let me know if you have any other questions.