Right now if you want voice synthesis (TTS) from Home Assistant your choices are Mary TTS which sounds like something from the 80’s, or cloud based spyware such as Google TTS.
Mimic 3 is a private, FOSS, local only (no cloud!) TTS option. It’s already compatible with Mary TTS, so HA can already talk to a Mimic server. There’s just no easy way to install it in Home Assistant.
An add-on would do just that!