Hi @123 , I wrote a custom integration called Chime TTS which is written in Python.
It adds a new service (chime_tts.say) to Home Assistant which allows you join audio files before and/or after TTS audio to form a new local mp3 file, played in a single service call to your media_player/s without any lag.
The service is configurable, so you can do things like specify how long of a delay you want to insert between the audio and TTS, change the speed of the TTS audio, and supports the various language-specific parameters available in Google Translate’s and Nabu Casa’s TTS services.