Ask HN: Are there any OSS online course platforms if I don't care about grading?

I'm part of a program right now developed by a psychotherapist. He has created dozens of hours of audio content meant to be consumed in a group setting over the course of a year. For every cohort, he screens people and puts the groups together (multiple groups run alongside each other using the same content for each cohort), and then every week the groups each meet and talk about the week's recordings. He also shares documents and links to other resources each week.

Currently, this is all being done by posting a links to all the audio sessions in a forum every week. It's clunky. It looks unprofessional, even though he's world-class at creating the content of the sessions.

I want to help him modernize it, but thinks like Moodle and Canvas are SO overkill for this need.

I'm looking for something lighter weight, self-hostable, and free. I'll do the work of setting it up and converting his existing materials, but I'm having trouble finding anything like this, even though this doesn't seem like that unusual of an approach.

What have you seen that works well?