I guess, I found a solution.
There is a freetts.com website allowed you to convert text to mp3
in many different languages and download mp3.
Than this mp3 file(s) could be stored locally on a hub and played to
the Symfonisk (sonos) speakers.
URI : http://hub_ip/local/filename works very well.
Somebody mentioned for the /local/ hub file location
just /local/finame should work but it does not.
Is this shortcut actually correct?
I am OK to use http://hub_ip/local/filename but it will
be nice if this string could be shorter.
I do this in one of my drivers - it has to be one of the names in the AWS Polly List. You can see them from Hubitat Settings --> Default Text To Speech . Just the name.
Sorry, the speak(text, volume, voice) is groovy so that was my context. You'd have to look in RM's dropdowns to see if uses the optional argument. My memory says no. I think that is one reason I wrote my driver.
as always most anything can be called via custom actions, however I'm 99% sure that it's being added or will be added to RM5.1 as an option to the existing Speak action, but don't shoot me if it doesn't appear in a 2.2.9.x release...