I'm easily able to pair an external BT speaker to my XPS 13 running UbuntuGnome 17.10. But...
1. I can't get any sound out of it. I see it in the sound panel and can do a speaker test, but no sound from the speaker during the test, or from any other app.
2. As soon as I try to route sound to the BT speaker, the wifi dies. Still connected, but anything using the wifi stalls out - streaming music, youtube, etc. Disable the speaker, wifi comes back.