Google/Baidu, universities, and an assortment of Chinese/Japanese/Korean social media companies (Line, etc.) are posting the most compelling TTS research, models, and code. Mozilla's TTS system [2] is an amalgam of some of these models, but it lags pretty far behind state of the art.
Mozilla should focus on getting additional revenue streams. We can help them out by trying to get Congress / DOJ to strip Google of its ability to have and maintain a browser with which they entrench their search and advertising moat. I think they're clearly in antitrust/anticompetitive territory.
[1] I'm pretty familiar with this field as I wrote https://vo.codes and https://trumped.com TTS systems. Neither of those are state of the art in terms of mean opinion score (MOS), but they're incredibly efficient.