There's a recent great article on TTS engines here.
https://www.mobileread.com/forums/sh...ght=read+aloud
I've tried to research available software, offline and online ones.
The question is what do you use actively yourself, and
what functionality you're not satisfied.
Me personally tried the one available in Calibre Reader. And had some issues with UI/UX more, rather than the speech quality itself.