Spotify Connect is now enabled for free-tier subscribers (it was a Premium perk until now). You will need to update the firmware of your smart speaker to get support, though.
Connect allows certain smarter than average speakers to stream music directly from the Internet, instead of using your phone as a middleman and playing over Bluetooth. You can see the list of compatible devices here.
The free tier still doesnt have access to the highest quality audio that Spotify offers, but at least this saves you any additional quality loss from Bluetooth. Heres a quick overview of how Spotify Connect works: