Does anyone have any experience with HuggingFace TTS models in Firefox? I know that there is a mobile application that allows you to change your default TTS engine to one of the models. I also know of an old method to get different, better-sounding TTS to work in Firefox. I think I was also able to get the Microsoft voices working through the same method with some workarounds, but I’m unable to provide a link. Any advice would be much appreciated.
That’s not quite how this all works. For local TTS you need specific boundaries and pre-trained models that can load, run, and interface with the local API of whatever your TTS system is.You can see a bunch here.
Then you have some like this that can run on espeak-ng, which should be a drop in TTS option for Firefox.
I know Read Aloud had some local options a bot ago, not sure how good they are.

