This is complicated. I'm not sure I would say it's not available, unless your meaning is with completely native integration. It is not currently available with an official integration, but it is possible to make Alexa speak based on a sensor input. I use this method. It requires the use of the SmartThings cloud and it requires Google Assistant Relay, which requires a node.js server running on your network. I did say it's complicated, but not currently available really depends on your definition.
Download the Hubitat app
