Unfortunately your guide links to stuff on adafruit that's out of stock - mostly the screen/microprocessor...

I found this guide that has a walk through with full code and an easy to use library for making the interface quite a bit better:

https://www.makerguides.com/digital-clock-crowpanel-3-5-display/

I'm going to be building two initially for myself and my girlfriends kid but once I work out the details I'll post it up on the fediverse somewhere with the full code to get going.

I am much more keen to use C instead of Python for something like a clock although I'm sure circuit-python is fast enough, id rather stick to native libraries.