Not sure if you got this working but I just add the on_tts_end part, I don’t have the on_tts_start in my config and it works perfectly with my Korvo-1, see below. Don’t forget to enable to configure the device to allow it to make action (service) calls as stated a few posts up…
on_tts_stream_start:
- lambda: id(voice_assistant_phase) = ${voice_assist_replying_phase_id};
on_tts_end:
- homeassistant.service:
service: media_player.play_media
data:
entity_id: media_player..output_speaker
media_content_id: !lambda 'return x;'
media_content_type: music
announce: "true"
on_tts_stream_end:
- lambda: id(voice_assistant_phase) = ${voice_assist_idle_phase_id};
on_end: