Mr Red wrote: Malware that transfers stolen data using Inaudible Audio signals from 2013

That relied on the target computer being compromised - infected by malware. You need physical access, social engineering - or a memory stick to do that.

Or a supply-chain compromise - increasingly popular - where a piece of software is updated that has been infected. Recently, malicious code has been inserted into widely used open-source modules. Imagine: a well-funded state actor starts an open source project to develop a development framework, which is so good it's widely adopted. Some years later it's found to include designed-in malware for spying.

I remember there was a case where data was exfiltrated from a non- compromised systen by tuning in to the electromagnetic radiation emitted by CRT VDUs. Someone in a van outside an office could reproduce the images on a screen being viewed inside. But they couldn't control what was being viewed.

But I don't recall a case where malware was installed onto a computer over an air-gap.