Many years ago I jailbreaked mine and used it as a display for a RPi Zero via VNC (
this guide). I wanted to embed the Pi inside the case somehow. Then I messed something and lost the JB and was unable to do it again.
Soon I will follow your steps and try again. I'm hoping to figure out a way to give it internet access and be able to sync progress in KoReader. Probably using usbNetwork backed by a small SBC.
To use the CDMA modem port would be awesome, but it is probably outside my capabilities.