Not sure if this thread is still followed, but thought I would mention …
I just developed a new SoundTouchPlus custom component if you’re interested. It can easily be installed via HACS as well. More information can be found in this forum post.
It supports the snapshot store / restore functionality, as well as extended source_select processing for both source= and sourceaccount= values required by Bose SoundTouch devices.
It also supports a Play TTS custom service that plays a Google TTS message via a service call and automatically resumes playing of previous source (no snapshot store / restore required). Note that the notification functionality is only supported on the ST-10,20,30 devices and NOT the ST-300 for some odd reason (Bose limitation, not mine). Example:
service: soundtouchplus.play_tts
data:
entity_id: media_player.soundtouch_10
message: Hello World, this is a TTS notification message
artist: TTS Notification
album: Google TTS
track: Hello World
tts_url: >-
http://translate.google.com/translate_tts?ie=UTF-8&tl=EN&client=tw-ob&q={saytext}
volume_level: 50
Hope it helps!