I really like OpenAudible for downloading, converting, and splitting, but I don’t like it for organization. For organizational purposes I’ve been self-hosting my audiobooks via
Audiobookshelf, ABS, on my always on M3 iMac. I like doing this because I also have audiobooks from other sources like Kickstarter, Humble Bundle, and Podiobooks from back when Podiobooks was a thing.
For me ABS is Calibre for audiobooks. It’s not for everyone and setting up Docker can be difficult if you’ve never done it before. ABS’ Discord server walked me through how to set up Docker. It was easy once I had a better understanding of how Docker works.