Dreammachines have a speaker and LED's that can be easily controlled with simple commands.
Thus, it is possible to play a WAV file with the following command aplay -l ding.wav
and to play with the lights with this other command.
Link: https://www.reddit.com/r/Ubiquiti/comments/i928s7/that_speaker_in_the_dream_machine_you_can_do/
Put the Wav files in the /mnt/persistent
directory of the DreamMachine.
On the Home Assistant side, put this in the configuration: