Quoting from our paper, training was done using "205 hours of 16-kHz speech from a combination of TTS datasets including more than 900 speakers in 34 languages and dialects". Mostly tested with English, but part of the idea of releasing early (none of that is standardized) is for people to try it out and report any issues.

There's about equal male and female speakers, though codecs always have slight perceptual quality biases (in either direction) that depend on the pitch. Oh, and everything here is speech only.