Hi Wangpy,
updated :08/07/23
The MIC+ have no jack detection system (unlike the ULTRA+) so it’s not possible to mute the speaker by software. Nevertheless it is possible to disconnect the hardware, to do so on the back of the board you have 2 labels on the back of the board ‘JP3’ and ‘JP4’, using a sharp blade cut the track, if you need to revert the modification use a soldering iron to reestablish the connection.