I use my old google nest speakers på send some notifications and it has been working fine until a few months ago.
Lately the volume control is all over the place.
One day it will be just a whisper and some days it will be full volume.
In the automation I try to first set volume to 50% and after that send the message, but that set volume action seams to do nothing permanent or fail.
So, it would be much better if the send notification action also had an option for volume level, just as the action turn on light can specify brightness and light color.