Linux

espeak default voice backend is synthesized without using actually real voice samples. So it doesn't require downloading a huge package for each language, which is convenient in some cases, but the outcome is extremely robotic.

You can use MBROLA as backend for espeak so that it uses some voice samples and the result should be less jarring (it'd still be easy to tell it's not natural voice, but at least you'd be able to understand it better). There's a tutorial on this here: https://github.com/espeak-ng/espeak-ng/blob/master/docs/mbrola.md

Or you can try piper (https://github.com/rhasspy/piper) it's one of the most natural-sounding TTS (here are some samples).

In addition to the very insightful reply by Ferk: Sadly most TTS development seems to be happening as online service these days. Google Neural TTS and Microsoft Azure TTS sound really great but require an online connection, an account, and possibly even paying (there's a threshold until it's free, then it costs almost nothing but almost nothing isn't free).

Btw, I don't know about the blind people you know but the ones I know use so insanle fast TTS output, the "sounds nice" aspect isn't really there in the first place. At least not to me.

Here is one of the best

https://github.com/neonbjb/tortoise-tts

A few days ago I wrote down a couple of links to interesting TTS projects that I was going to look into whenever I have time, along with some brief notes.

https://github.com/coqui-ai/TTS TTS + XTTS, GPU inference? 3GB model.

https://github.com/rhasspy/piper Low resource, CPU inference. 50MB model.

https://github.com/p0p4k/vits2_pytorch GPU inference? 500MB model. https://github.com/p0p4k/vits2_pytorch/discussions/27 Someone's models for vits2

I've recently made aware of the bark project. Especially the bark-ui project. It takes a long time to run but it does work. Sometimes it makes cursed stuff too: https://social.rootaccess.org/@michaelc/111277260439738652

https://github.com/mozilla/DeepSpeech the best quality available that I've seen

Not sure if this is gonna be much better than the alternatives you've listed, but you can try adjusting pitch, rate, range, etc. with spd-say.

If you don't mind doing some development work, needing online connectivity, and paying for usage, AWS's Polly has some very good sounding TTS voices: https://aws.amazon.com/polly/

Samsung's TTS engine for android is the best I have found. I use it to listen to epub books.