Jim, no need to record analog output – I am dubious that will provide the level precision necessary for some comparisons. However, last spring, I used the Tidal desktop app and ancillary software to create some bit perfect 30 second captures of Tidal streams, both HiFi and MQA. I then ran DR metrics on those captures. See several of my posts in this thread (you will need to scroll to find all posts with capture data):
In short, level or mastering differences in some cases, no differences in other cases – as was expected. But the real takeaway is that digital domain comparison is possible and relatively easy to accomplish.