Don’t connect it. I bought one for this purpose and it updated to a version that didn’t have a known jailbreak

Depends on the firmware of the device. Latest firmware (anything after version 5.18.5.01 - which released in October 2025) is currently not jailbreakable.

Jailbreak of any firmware after version 5.16.2.1.1 (June 2023) requires the Kindle to be connected and registered.

Anything prior to, and including this version, can be jailbroken with no registration.

I don't believe you need internet connection - IRRC jailbreaking steps were plug in the Kindle, drop the jailbreak folder into the root directory, then choose `Update` from the Settings screen.

The hardest part was finding the `Update` menu item. It's only visible if you go to Settings, then press the menu button again while on the Settings page.

Not sure if registering the Kindle was required.