The display coming with the Photon Maker Kit is a SPI/I2C 128x64 OLED (SSD1306 compatible) that can be used either way, but comes preconfigured as SPI.
To turn it into an I2C device you’d only need to bridge on jumper on the bottom side of the PCB.
The other thread referenced above has grown a bit further and could be marked as solved (which I’m going to do right now ;-))
Near the bottom of the thread (#36ff) you’ll find some snaps of a working setup and in the preceeding posts the hints to get things running.