On the RPI 5 and some base bords for the CM5 is a button “PSW”.
Obviously this button starts up the Pi from standbye, but if pressed while Volumio is running it seems to shut it down.
What I can find out, is that pressing this button while the sysem is on it initiates a safe gracefull shutdown at OS level.
question: Is this the same as selecting shutdown from the Volumio menu. ie doing all the things that volumio need to shutdown without coruption etc.