It's there :)
volumio@volumio:~$ amixer contents -c D10s
numid=4,iface=CARD,name='Topping Internal Clock Validity'
; type=BOOLEAN,access=r-------,values=1
: values=on
numid=2,iface=MIXER,name='D10s Playback Switch'
; type=BOOLEAN,access=rw------,values=1
: values=on...