A simple project has shown that the Raspberry Pi can, in conjunction with a Bluetooth speaker, become an Alexa-enabled device. There is no restriction on what type of Bluetooth speaker can be used, allowing a great deal of customisation with the project.
https://www.notebookcheck.net/Raspberry-Pi-Transform-the-popular-single-board-computer-into-an-Amazon-Alexa-home-hub.498873.0.html