Obvious solution, don't use anything that emits electromagnetic radiation: https://en.m.wikipedia.org/wiki/Van_Eck_phreaking

Well, time to go back to typing everything on a typewriter.

Your data will leak regardless because of typewriter keystroke acoustics [0]. So you better have a soundproof room for that purpose.

Keep any electronics out of the room that might have a microphone. Like phones, laptops, or running mechanical hard drives [1].

[0]: https://arxiv.org/abs/1609.09359

[1]: https://spqr.eecs.umich.edu/papers/Kwong-HDDphone-IEEE-SP-20...

Well you can avoid all software vulnerabilities by not using computers at all, right?

Maybe I should use an Ethernet cable on my iPhone instead of LTE, that should be convenient.

As soon as people stop treating the physical layer as a security control, the better.

Encrypt your damn comms.