No need, just summon the Google Assistant in your phone and ask it to
"Cast Settings" you'll find a list of your speaker groups and will be
able to cast phone's audio to any group there
There's a more simple and effective workaround that has been posted
multiple times already in this discussion, via phone's assistant and the
Cast Settings command
Actually the best workoaround is the one mentioned multiple times
here..And is to activate Google assistant on your phone and either
verbally tell it or type : cast settingsIt will open a new window from
which you can cast your phone's audio to speak...
