Built my Zynthian but the screen display is upside down, ending with a summary and article on displays, I2C and SPI

Burn the image again. Revise all the connections and try again.
It should work out t the box. No further config is needed. Really!

If you see the display rotated, the system is not booting ok. FYI, the display is mounted physically rotated in the V5 and the software takes care of this. If the system is not booting OK, then you will see the display inverted.

Regards