I thought John Deere would be able to remotely shut them down
No joke, you can actually jailbreak your tractor 😂 https://www.wired.com/story/john-deere-tractor-jailbreak-defcon-2022/
but you cannot jailbreak your new spiphone (easily)any more. you could until about ten years ago. it was no issue. now you have to use special tools and you will run a different operating system which you will need to trust: https://pangu8.com/jailbreak/ if you need to JAILbreak your device, what does this word imply where you are?
Tesla jailbreaks would be awesome.