I have a new Alexa enabled Sonos beam connected to a Samsung TV. In addition we have 3 other Sonos speakers. If we ask Alexa to stream music from one of the named speakers, for example, kitchen, it only plays it on that device and stops it on the beam. If we set up groups in the Alexa app (as is suggested) then these seem to become the default - for example set up a group to include the beam, kitchen and dining room and from then on all music automatically streamed through all 3. Our desired set up is:
Beam (named Lounge) on its own as default
Group of beam in lounge, dining room and kitchen as a group to be able to be requested but not default
Additional groups if possible, but when attempting to set up additional groups can to add beam as preferred speaker.