Ideally we should just let the government write the software, and they'd be able to verify that there's no dangers to grandma anywhere in the system.

It would be foolproof, maybe the most trustworthy system ever conceived.

While we're at it, let's also mandate the destruction of every general-purpose computing device incapable of secure boot or allowing it to be deactivated. And if someone dares to build a homebrew CPU out of relays, transistors, or logic ICs, they should expect the FBI to break down their door.