Today I did an experiment with MQA. I purchased the MQA 'Studio' version of "To Bethlehem Carols and Motets" from the HighResAudio site. That went well, so I converted a couple of the FLACs (24/48, which 'unfold' etc. to 24/96 in an MQA player or a full decoding MQA DAC) to MP3. I played the MP3s on the free Vox player (not an MQA player) into the DragonFly Red DAC from my Macbook, making sure that the MIDI setting was 24/48.
The DF Red is just a renderer, not a full decoder, yet the DF light turned blue for high-res MQA. Note that if my MIDI setting was anything but 24/48, the light would not turn blue. Not on the DF nor the Meridian Explorer, which is a full decoding DAC.
So, the ability to enable a form of DRM is present in the music file, even when converted to a foreign format like MP3. Of course I could set the MIDI setting to another value to defeat the blue light, and MP3 playback wouldn't care about that, but I suppose that newer firmware updates on popular DACs might be able to detect an MQA file anyway, no matter the resolution settings on the computer or the converted file type.
At this point I have to conclude that the only safe way to avoid DRM (if it happens, or happens with MQA) is to use a non-MQA music player, preferably an open-source player.
In spite of that precaution, if an MQA firmware update to any of the popular DACs can always detect an MQA file (as it apparently can now), the DAC could refuse full-res or proper playback under some circumstances, even when using an open-source player.