The slide decks are working fine as of now, but the GitHub site is completely FUBAR when it comes to rendering Notebooks over the wire. This isn't the first time GitHub has interrupted its service w/r to said file type (ipynb). Usually the situation gets resolved but we're coming up on a Week of Snafu.
So, my advice is to clone the repos you need and project them locally. Encourage your students to do the same.
Jupyter Notebooks are meant to be interactive.
I have a lot of em wired to Colab versions of themselves, for those with Google Drives, and you're welcome to use some other online Docker-like solution (meaning you'll be running a Jupyter server in the cloud). nbviewer tends to throttle my account, prolly cuz they don't like me using their free service much.
A better solution than relying on weak links in the cloud, is to have the repos locally and to call the Notebooks up within your own local copy of JupyterLab.
I recommend grabbing and installing the Anaconda distro for all this, including the Python interpreter itself.
However you may have a preferred stack starting with the official Python, then maybe uv and PyPi (Python Package Index) for adding 3rd party packages (such as JupyterLab).
Here's my Anaconda Navigator as of right now:
