I have already searched the forums and elsewhere online about this.
It seems that one way to sideload audiobooks is to zip up some MP3 files, and rename the extension from ZIP to MP3Z. This works, but invokes a very basic audio player on my Clara 2E. Also, the listing does not show any metadata.
I understand that an official audiobook from Kobo invokes a fancier audio player, and shows metadata in the listing.
An old forum posting indicated that someone had success sideloading an audiobook by creating an MP4 file with an M4B extension.
I tried this with both an audiobook that I created from MP3 files, using this program:
http://www.audiobookcreator.de/en/index.html, and one I downloaded from Internet Archive (already in M4B format). Neither of the M4B files get added to My Books on the Clara 2E.
I also tried adding the files in the root folder, and an Audiobook folder. That doesn't work, either. Even a power off/on doesn't force the adding of these files.
Does anyone know what the secret is to creating an audiobook like the ones that you buy from Kobo? Does anyone have a free PD Kobo audiobook that they can share, so I can try that one?