Make iTunes recognize MP3 audiobooks with ID3 tag
No, there is no documented way to mark MP3 files with ID3v2 tag as audiobooks in a way that Apple products (or any hardware or software player really) would understand. There apparently is also no undocumented way known either.

Although there is a public Github repository, the development of ID3v2 has stalled for over a decade now and should not be expected to be picked up ever again, because more recent container formats, like MOV-based Part-14 MP4, use different metadata formats.