To anyone to whom this is not obvious, it should be noted that TWRP includes adb in root mode. So if you want to have console root on the phone just to snoop around and look at things, the quickest way is:
- unlock the bootloader
- fastboot boot twrp.img
- adb shell
- mount system and vendor read only as seen necessary
no flashing or any eeprom modification needed.
Unfortunately the TWRP minimal busybox does not include any wifi drivers or tools, so no networking.
How hard is it to go from TWRP to a minimal ubuntu/debian image? If one places the ubuntu system image within the userdata partition, no flashing of the phone would have to happen (as long as one boots via fastboot and external boot image)