gPodder does ship with a command-line interface "gpo" that can just do the subscribing and downloading part which might suit your needs (while still retaining the possibility to bring up the GUI if needed, the on-disk format is the same).

If you roll your own, https://github.com/gpodder/podcastparser is a neat little Python library that has been split out from (and is now used by) gPodder, as dealing with all kinds of RSS (and Atom) specialities is kind of something you want to outsource if possible.

I'll check out `gpo`, thank you. To be honest the other reason for this was an exercise in Haskell a while ago, and an exercise in Python long, long ago before that. I'm beyond that interest these days so something that doesn't break constantly sounds like a good plan.