Primarily based off this guide

SD swap

Image with dd, bs=4m (lowercase m on macOS)

Reformat kobo_sdcard.img to new SD card

Resize/reformat third partition to fill remaining space - ereader will only show 8GB total otherwise!

Registration

Select "Don't have a WiFi network?" and connect ereader to a computer.

cd /Volumes/<kobo>/.kobo/
sqlite3 KoboReader.sqlite
INSERT INTO user(UserID,UserKey) VALUES('1','');

Developer mode

unlocks extra features including sudoku and unblock me

1. Search bar
2. Type "devmodeon"