I found this free speech-synthesis engine for Android:
https://k2-fsa.github.io/sherpa/onnx/tts/apk-engine.html
Pros:
- Many Languages
- Different voices
- Whisper AI based
- Works good for me
- Fully offline
- Open Source
Cons:
- Chinese developer with no credibility in the western world (yet)
I tried all the other engines (espeak, RHVoice, Google) and only Google really delivered a pleasant experience to me. I'm am tempted to dump Google for this one because the quality is pretty awesome.
What do you think? Is it a good choice?