Would you settle for as "horrible" as new open source TTS systems? :D

My current go to is Piper TTS: https://github.com/rhasspy/piper

It's MIT-licensed, supports ~30 languages and multiple voices[0]/quality/licenses.

Voice output samples: https://rhasspy.github.io/piper-samples/

Discovered just now that recently there's also been some efforts to train Public Domain/CC-BY licensed voices specifically for Piper TTS too: https://brycebeattie.com/files/tts/

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[0] e.g. One of the English voice sets has ~900 voices(!).