Why do you need to use Audacity for this? It looks like you should be able to do the entire task in “DifferentialEQ” 
DifferentialEQ cannot process audio. It can only compare audio files and export an EQ curve for use in Audacity. If I can find a legit replacement for this toolchain, I will happily consider it, though my search has turned up nothing comparable thus far. In the meantime, I’ve figured out how to have two different versions of Audacity running on my system at the same time: Audacity 3.0.3 compiled from source (Linux) and Audacity 2.3.2 for Windows running in Wine. So, as long as I can keep this old version running, my work can proceed unhindered.
You could also post a feature request here: https://github.com/audacity/audacity/issues
(I think the forum’s feature request board has become redundant, so better to post to GitHub)