Followup to "no status for serial::write" (#21577)

Marlin/src/core/serial_hook.h

   static constexpr uint8_t SecondOutput  = (Usage << (offset + step));
   static constexpr uint8_t Both          = FirstOutput | SecondOutput;
 
-  NO_INLINE size_t write(uint8_t c) {
-    size_t ret = 0;
-    if (portMask.enabled(FirstOutput))   ret = serial0.write(c);
-    if (portMask.enabled(SecondOutput))  ret = serial1.write(c) | ret;
-    return ret;
+  NO_INLINE void write(uint8_t c) {
+    if (portMask.enabled(FirstOutput))   serial0.write(c);
+    if (portMask.enabled(SecondOutput))  serial1.write(c);
   }
   NO_INLINE void msgDone() {
     if (portMask.enabled(FirstOutput))   serial0.msgDone();

Marlin/src/feature/meatpack.h

   uint8_t charCount;
   uint8_t readIndex;
 
-  NO_INLINE size_t write(uint8_t c)   { return out.write(c); }
+  NO_INLINE void write(uint8_t c)     { out.write(c); }
   void flush()                        { out.flush();  }
   void begin(long br)                 { out.begin(br); readIndex = 0; }
   void end()                          { out.end(); }

buildroot/tests/mega2560

 # Test Laser features with 12864 LCD
 #
 restore_configs
-opt_set MOTHERBOARD BOARD_RAMPS_14_EFB LCD_LANGUAGE en TEMP_SENSOR_COOLER 1 EXTRUDERS 0 TEMP_SENSOR_1 0
+opt_set MOTHERBOARD BOARD_RAMPS_14_EFB LCD_LANGUAGE en TEMP_SENSOR_COOLER 1 EXTRUDERS 0 TEMP_SENSOR_1 0 SERIAL_PORT_2 2
 opt_enable REPRAP_DISCOUNT_FULL_GRAPHIC_SMART_CONTROLLER SDSUPPORT EEPROM_SETTINGS EEPROM_BOOT_SILENT EEPROM_AUTO_INIT \
-           LASER_FEATURE LASER_COOLANT_FLOW_METER
+           LASER_FEATURE LASER_COOLANT_FLOW_METER MEATPACK_ON_SERIAL_PORT_1
 
-exec_test $1 $2 "REPRAP MEGA2560 RAMPS | Laser Feature | Cooler | Flowmeter | 12864 LCD " "$3"
+exec_test $1 $2 "REPRAP MEGA2560 RAMPS | Laser Feature | Cooler | Flowmeter | 12864 LCD | meatpack | SERIAL_PORT_2 " "$3"
 
 #
 # Test Laser features with 44780 LCD