I recently purchased the Q800B Soundbar and an Alexa Echo. I'm very disappointed to see that the issue first raised in 2020 (this thread) is still not resolved in 2023.
Even more disappointing, that previous issue thread is marked as "solved" even though the "solution" is:
The functionality of adding your sound bar to an Alexa speaker group is not currently supported. This suggestion has been forwarded to our engineers, but I have no information as to when this might be added, or if it even can be added.
Stating that "we will look into the issue" is not a solution!