Audiobook m4b format not working

Hi all,

I'm having issues with playing audiobooks in the m4b format on my Garmin Fenix 7 Solar.
I can play mp3 files, but I would much prefer m4b files as they contain chapters, and thereby I only need to manage 1 file per audiobook and eliminate a file conversion process as well.

Having looked at the support article here, the format should be supported by Garmin: link

Have one of you found a solution to this?
Or have you successfully played an m4b file on the watch?

Thanks

*I started this question in the Beta forum, but got a good suggestion to ask here as well.