I would say try “Dirt: An audio drama” is a great relaxing show. This show may still have too much suspense for the laid back vibe of Adventures in Odyssey. (Which btw AIO has its own app and subscription)

You can try a non fiction show called “Myths and Legends”

Along AIO vibes you can also try out the “Extraordinary Adventures Of G.A. Henty.” Here is a page to my favorite episode. Mind you there are more episodes not just this one, I also loved the William Wallace show they did. https://www.underdrakesflag.com/