Hey Pixmusix,
From what I can tell from the code used in this link they are using a big if/else statement to determine what board is being used before they import the required library.
Looking at the documentation for SD card use in MicroPython I think this library call method is incorrect. I think it should be
import os
import machine
import sdcard
With ‘sdcard’ being called in lowercase and as a separate library.
The documentation at the below link made sense to me, hopefully you can make use of it:
Hopefully this helps you out!
Sam