The USB port on the My Cloud is generally for attaching USB hard drives not for attaching things like a Bluetooth USB dongle (or similar BT device).
I have seen some mention using a Sonos device (https://www.sonos.com/) to supposedly access an NAS directly to play music without going through a third device. But not sure how that works exactly.
Unfortunately most of the BT devices will require a third party device to act as the intermediary between the BT device and the My Cloud.
For the Amazon Echo one can use the Plex media server on a computer (or similar device) to bridge between the Echo and the My Cloud. One could try installing the Plex media server to second gen versions of the single bay My Cloud via the apps hack (see this link). One would also have to install the Plex Skill on the Echo. The main reason I don’t go this route is to use Plex in this fashion requires having to have Plex connect to the internet so it can then stream music to the Echo. I typically prefer to not to have my music/content/data leaving my local network when going from one local device to another local device.
Or one could use an old smartphone that has both WiFi and BT capability and stream from the cell phone to the BT speaker or Echo.
If one has a spare computer or laptop they could install a BT USB dongle to the device if it doesn’t already have BT and use that computer/laptop to stream content directly to the BT speaker.
Most newer soundbars also have BT capability so if one has a soundbar check to see if it has BT capability. It would avoid having to buy a dedicated BT speaker.
Currently I use the BT on an Amazon Echo in two ways. One is using an old smartphone to stream media content either from the phone or from the My Cloud direct to the Echo. I also have a laptop with a BT USB dongle that is also paired with the Echo. I then stream content from the My Cloud via the PC to the Echo.
On a side note I also have a sound bar that gets a Roku piped through it (via HDMI) so I can stream any DLNA content from the My Cloud through the sound bar.
There are options but unless the BT device allows for mapping/accessing the My Cloud directly one will be forced to use an intermediary device to make the connection between the My Cloud and the speakers.
