When I was toying around with making my own voice assistant, I used Mimic 3 and found that to have quite nice voices.
Nowadays there's voice cloning from only a few seconds of audio. Type "!gh tts" in duck.com and you get a list of repos. You can sort by the number of stars. Other than voice cloning, there are some options that seemed promising. O haven't tried any, that's why I share this comment in such a 'raw' format. Good luck! Please come back and share your thoughts on what you found out...
Have you browsed the list of speech a dispatcher back-ends, and the different voices available for each of them?
RHVoice
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