The executive summary is worth the 1-minute read.
Interesting that all the malicious frameworks known (by ESET) that target air-gapped networks were for some form of espionage.
Also interesting that "All the frameworks used USB drives as the physical transmission medium to transfer data in and out of the targeted air-gapped networks. We have not found any case of actual or suspected use of covert physical transmission mediums, such as acoustic or electromagnetic signals."
Probably because to get this stuff to work is really hard in practice.
Several years ago, we were playing with https://github.com/fulldecent/system-bus-radio to work, but we couldn't, even though we had the right MacBooks.