I stumbled upon streamripper which is a command line tool to do what the tool name says. And apparently there's a docker container available to play around: https://hub.docker.com/r/clue/streamripper

The container in its current shape is not exactly fit for the purpose of recording the streams on a a predefined schedule. But you can start it with supplied parameters (streamripper command line params), and as a result you get the file saved to your location. So in a way it does the job, but you need to automate container management (start time, etc) for that purpose.

I may explore the idea of creating a more flexible container using streamripper once I have more time.

Audiobookshelf can download/play/manage podcasts too, not only Audiobooks.

Podfetch also exists.

Simply searching this sub and looking at the awesome-selfhosted list linked in the sidebar would have given you these and more options.