It’s not for a production-type thing but Home Assistant has this pipeline built in and you can swap out any of the 3 steps:

* STT

* LLM

* TTS

It’s pretty cool to be able to replace one of the parts, do some tests, then change another part.

Again, it’s nothing you would use directly for a product but it’s fairly easy to test your pipeline by plugging into different aspects. (Also HA provides each component out of the box if you want them to handle STT/TTS and just test your LLM).