Regarding Amazon's files: "Both types of HD audio will stream as uncompressed FLAC rather than the MQA format used on Tidal."
From Extreme Tech: https://www.extremetech.com/internet/298538-amazon-pulls-the-rug-out-from-under-tidal-with-new-hd-music-streaming-service
From Extreme Tech: https://www.extremetech.com/internet/298538-amazon-pulls-the-rug-out-from-under-tidal-with-new-hd-music-streaming-service