I use "kokoro-tts" CLI, which has better chunking/splitting.

https://github.com/nazdridoy/kokoro-tts

It generates a directory of audio files, along with a metadata file for ebook chapters

You have to use m4b-tool to stitch the audio files together into an audiobook and include the chapter metadata, but it works great:

https://github.com/sandreas/m4b-tool

I've been meaning to write a post on this workflow because it's incredibly useful