Changing the output device doesn’t seem to make a difference. Bluetooth works, speakers don’t.
(What can I do on the keyboard? I’m not aware of any ‘mute/volume actions that may have happened, cat involvement or not.)
Every keyboard has dual function use of the F keys at the top. Most Linux support these and have drivers for these also. Some control screen brightness and there should be a mute button and volume up and down options. If for some reason the Function key at the bottom is pushed simultaneously as a top F key it will activate these function key options. They are mechanical control options that override any software settings. Had someone the other day who lost their top and bottom bars, it was just the cat walked over the keyboard and stepped on the F11 key which hides these of course so that is why I joked about the cat. Not saying that is it but it is worth checking to make sure one of these key controls is not the problem.
In the mean time I am looking to see if anyone else had the same issue with the update.:)