My understanding is that Mozilla is continuing to build the CommonVoice dataset for training speech models, but they are no longer developing TTS or STT software themselves.

https://github.com/coqui-ai/TTS is the new home of what was Mozilla's TTS project. Coqui is a new company where some of the former mozilla speech team ended up. Coqui is continuing to develop both the TTS and STT code and models.

• https://tts.readthedocs.io/en/latest/
• https://stt.readthedocs.io/en/latest/

There are a number of other much older free software TTS options, but Coqui's (formerly Mozilla's) is by far the best one I've heard.