This is a “note to self” type post, and basically because Google seems unable to find a direct answer to this simple question.
So it’s simple as this
# configure
(config)# interface ethernet NN
(config-if)# no channel-group
et voilà, the ethernet port doesn’t belong anymore to the port channel. It should work with PowerConnect 5324, PowerConnect 5424, PowerConnect 5448, PowerConnect 5548 etc.
The eternal fight between admins and computers 
Thank you for posting this . It also works with N4x series where to add a port channel, you go into interface range but to remove- one needs to go into individual interfaces.