Yep, I had to get deep into OIDC for OpenPubkey and it basically involved me having to build teaching materials and notes for myself. I had a bunch of Google docs slides I consult every time I got confused about what something did. A major motivation for writing the OpenPubkey paper was to have detailed notes on how OIDC works to remind myself.

I recommend sections I and II of the OpenPubkey paper to anyone trying to understand OIDC public clients. I consult it at least once a month: https://eprint.iacr.org/2023/296