There are tons of ways to make air gappped systems transmit data. They all include the installation of some malware and have become more expensive and less usable over time.

Back in the day with crt screens you could just capture the frequencies transmitted when creating the picture and look at the copy straight away.

No malware. No direct contact. And it worked over rather big distances.

The same thing killed electronic voting machines in The Netherlands.

No matter how well you argue that it is "perfectly secure", when some nerd outside the polling station is showing reporters a real-time feed of who people are voting for, your machine will get thrown out.

It wasn't quite CRT-level of mirroring, but it wasn't far off...