Rockbox is lovely software, if you have time to set it up properly and are interested in reading manual with over 100 pages.
Not something really suited for common customer.
But if there is some group interested into adopting Rockbox to M0, I will do my best to help them with it.
Thank you, will try to find out more about it.
Not sure who Fiio contacted.
On our side, we want to make basic audiobook/podcasts app, with key features like bookmarking, remembering positions for each file, controlling the speed of playback.
So any audiobook you have in MP3 from whatever source, or podcast you just downloaded from soundcloud, will work.
If you are using audiobooks from some closed system and with DRM, there the chances are quite limited. These big players keeping their "treasure" safe are not interested into third party apps, especially since it's some unknown device for small market.
For the same reason you will likely never see Spotify support outside of Android DAPs.