max7219 chained display showing mirrored text
Since version 3.0 MD_MAX72xx.h no longer supports that definition. Now the hardware type is defined as a parameter on creation (in the "Example" file you are using - not in MD_MAX72xx.h)

#define HARDWARE_TYPE MD_MAX72XX::FC16_HW
...
MD_Parola P = MD_Parola(HARDWARE_TYPE, CS_PIN, MAX_DEVICES);


Note that I've changed the hardware type from PAROLA_HW to FC_16.