Hmm, I’ve found something else in the logs that might be related
Logger: homeassistant.components.cast.media_player
Source: components/cast/media_player.py:405
integration: Google Cast (documentation, issues)
First occurred: September 18, 2024 at 11:37:41 AM (14 occurrences)
Last logged: 7:55:42 AM
Have your tried tts.speak also (piper and local)? Does anything work when going to dev tools > actions > choosing tts.cloud_speak or tts.google_speak, then choosing the device and typing in some text to see if that works?