Not being able to play a file from Amazon (or any other service) offline has nothing to do with MQA.
The only “DRM” in MQA relates to authenticating the file (i.e. turning on the “MQA” indicator) NOT in actually replaying it.
If you buy an MQA file (there are places that sell them), it will play in ANY standard PCM-capable FLAC player to any standard PCM-capable DAC without issue, regardless of whether it has an internet connection or not, and without any restrictions on being copied.
Other than some data “encoded” in the three LSBs of each sample, MQA files can be treated as simple PCM files.
If you have an MQA-enabled software player (Roon, Audirvana, TIDAL’s client, etc.) then you get the “first unfold” done in software, which results in a higher bit-rate output (double the native resolution). Again, there is no need for any kind of connection to the internet, no phoning home, nothing … all you need is an MQA file and an MQA player and this will work.
If you want the “second unfold”, which is simply upsampling the data from the first unfold by 2x and then applying one of MQA’s specific reconstruction filters, you need an MQA-enabled DAC or DAP.
Again …
MQA files are just FLAC files and will play in any FLAC player to any PCM DAC.
If you want the first level of “MQA” capability you also need a software player that understands the embedded “MQA data” to decode it (which is no different to needing a specific player for any other file type, such as DSD).
If you want the “full MQA experience” then you need a DAC that can process MQA.
And if you have an MQA-enabled DAC or DAP, then it’s easy to tell if you’re getting “the full experience” because a little light or indicator will come on to tell you that.
Other than not really adding anything useful to the consumer, MQAs biggest problem is that people don’t understand it … not in any “restrictions” on what you do with the content once you have it.