diff --git a/Marlin/src/HAL/AVR/HAL.cpp b/Marlin/src/HAL/AVR/HAL.cpp
index 7c39c5200b..0527f3d8c5 100644
--- a/Marlin/src/HAL/AVR/HAL.cpp
+++ b/Marlin/src/HAL/AVR/HAL.cpp
@@ -88,6 +88,10 @@ void MarlinHAL::reboot() {
   #endif
 }
 
+// ------------------------
+// Free Memory Accessor
+// ------------------------
+
 #if ENABLED(SDSUPPORT)
 
   #include "../../sd/SdFatUtil.h"
diff --git a/Marlin/src/HAL/AVR/HAL.h b/Marlin/src/HAL/AVR/HAL.h
index d346041805..42ae521dfc 100644
--- a/Marlin/src/HAL/AVR/HAL.h
+++ b/Marlin/src/HAL/AVR/HAL.h
@@ -163,7 +163,7 @@ typedef Servo hal_servo_t;
 #define strtof strtod
 
 // ------------------------
-// Class Utilities
+// Free Memory Accessor
 // ------------------------
 
 #pragma GCC diagnostic push
diff --git a/Marlin/src/HAL/DUE/HAL.cpp b/Marlin/src/HAL/DUE/HAL.cpp
index bbd13dc05a..39a28359e5 100644
--- a/Marlin/src/HAL/DUE/HAL.cpp
+++ b/Marlin/src/HAL/DUE/HAL.cpp
@@ -40,14 +40,15 @@ uint16_t MarlinHAL::adc_result;
 // Public functions
 // ------------------------
 
-TERN_(POSTMORTEM_DEBUGGING, extern void install_min_serial());
+#if ENABLED(POSTMORTEM_DEBUGGING)
+  extern void install_min_serial();
+#endif
 
 void MarlinHAL::init() {
-  // Initialize the USB stack
   #if ENABLED(SDSUPPORT)
     OUT_WRITE(SDSS, HIGH);  // Try to set SDSS inactive before any other SPI users start up
   #endif
-  usb_task_init();
+  usb_task_init();          // Initialize the USB stack
   TERN_(POSTMORTEM_DEBUGGING, install_min_serial()); // Install the min serial handler
 }
 
@@ -72,6 +73,10 @@ uint8_t MarlinHAL::get_reset_source() {
 
 void MarlinHAL::reboot() { rstc_start_software_reset(RSTC); }
 
+// ------------------------
+// Free Memory Accessor
+// ------------------------
+
 extern "C" {
   extern unsigned int _ebss; // end of bss section
 }
@@ -82,6 +87,10 @@ int freeMemory() {
   return (int)&free_memory - (heap_end ?: (int)&_ebss);
 }
 
+// ------------------------
+// Serial Ports
+// ------------------------
+
 // Forward the default serial ports
 #if USING_HW_SERIAL0
   DefaultSerial1 MSerial0(false, Serial);
diff --git a/Marlin/src/HAL/DUE/HAL_SPI.cpp b/Marlin/src/HAL/DUE/HAL_SPI.cpp
index c5e8f2433d..7e3fe01356 100644
--- a/Marlin/src/HAL/DUE/HAL_SPI.cpp
+++ b/Marlin/src/HAL/DUE/HAL_SPI.cpp
@@ -31,8 +31,6 @@
 
 /**
  * HAL for Arduino Due and compatible (SAM3X8E)
- *
- * For ARDUINO_ARCH_SAM
  */
 
 #ifdef ARDUINO_ARCH_SAM
diff --git a/Marlin/src/HAL/HAL.h b/Marlin/src/HAL/HAL.h
index 0cd836af2b..2dda287ac7 100644
--- a/Marlin/src/HAL/HAL.h
+++ b/Marlin/src/HAL/HAL.h
@@ -28,6 +28,7 @@
 #endif
 
 #include HAL_PATH(.,HAL.h)
+extern MarlinHAL hal;
 
 #define HAL_ADC_RANGE _BV(HAL_ADC_RESOLUTION)
 
diff --git a/Marlin/src/HAL/LPC1768/HAL.h b/Marlin/src/HAL/LPC1768/HAL.h
index 0f26509129..d058de8720 100644
--- a/Marlin/src/HAL/LPC1768/HAL.h
+++ b/Marlin/src/HAL/LPC1768/HAL.h
@@ -177,7 +177,7 @@ void flashFirmware(const int16_t);
 #define CPU_ST7920_DELAY_3 750
 
 // ------------------------
-// Class Utilities
+// Free Memory Accessor
 // ------------------------
 
 #pragma GCC diagnostic push
diff --git a/Marlin/src/HAL/NATIVE_SIM/HAL.h b/Marlin/src/HAL/NATIVE_SIM/HAL.h
index 49a5b6ea56..35fce855cb 100644
--- a/Marlin/src/HAL/NATIVE_SIM/HAL.h
+++ b/Marlin/src/HAL/NATIVE_SIM/HAL.h
@@ -186,7 +186,7 @@ constexpr inline char* strstr_constexpr(char* str, const char* target) {
 }
 
 // ------------------------
-// Class Utilities
+// Free Memory Accessor
 // ------------------------
 
 #pragma GCC diagnostic push
diff --git a/Marlin/src/HAL/STM32/HAL.cpp b/Marlin/src/HAL/STM32/HAL.cpp
index 2d8b672c3d..7e410fff84 100644
--- a/Marlin/src/HAL/STM32/HAL.cpp
+++ b/Marlin/src/HAL/STM32/HAL.cpp
@@ -24,12 +24,11 @@
 
 #ifdef HAL_STM32
 
-#include "HAL.h"
-#include "usb_serial.h"
-
 #include "../../inc/MarlinConfig.h"
 #include "../shared/Delay.h"
 
+#include "usb_serial.h"
+
 #ifdef USBCON
   DefaultSerial1 MSerialUSB(false, SerialUSB);
 #endif
diff --git a/Marlin/src/HAL/STM32F1/HAL.cpp b/Marlin/src/HAL/STM32F1/HAL.cpp
index 636dc742fc..43ee91e490 100644
--- a/Marlin/src/HAL/STM32F1/HAL.cpp
+++ b/Marlin/src/HAL/STM32F1/HAL.cpp
@@ -83,6 +83,7 @@
 // ------------------------
 
 #if defined(SERIAL_USB) && !HAS_SD_HOST_DRIVE
+
   USBSerial SerialUSB;
   DefaultSerial1 MSerial0(true, SerialUSB);
 
@@ -211,6 +212,10 @@ void MarlinHAL::idletask() {
 
 void MarlinHAL::reboot() { nvic_sys_reset(); }
 
+// ------------------------
+// Free Memory Accessor
+// ------------------------
+
 extern "C" {
   extern unsigned int _ebss; // end of bss section
 }
@@ -243,9 +248,9 @@ extern "C" {
 }
 */
 
-//
+// ------------------------
 // ADC
-//
+// ------------------------
 
 enum ADCIndex : uint8_t {
   OPTITEM(HAS_TEMP_ADC_0, TEMP_0)
diff --git a/Marlin/src/HAL/TEENSY31_32/HAL.cpp b/Marlin/src/HAL/TEENSY31_32/HAL.cpp
index b923ab77b1..28c3fdc4d6 100644
--- a/Marlin/src/HAL/TEENSY31_32/HAL.cpp
+++ b/Marlin/src/HAL/TEENSY31_32/HAL.cpp
@@ -44,25 +44,6 @@
 #endif
 USBSerialType USBSerial(false, SerialUSB);
 
-// ------------------------
-// Class Utilities
-// ------------------------
-
-extern "C" {
-  extern char __bss_end;
-  extern char __heap_start;
-  extern void* __brkval;
-
-  int freeMemory() {
-    int free_memory;
-    if ((int)__brkval == 0)
-      free_memory = ((int)&free_memory) - ((int)&__bss_end);
-    else
-      free_memory = ((int)&free_memory) - ((int)__brkval);
-    return free_memory;
-  }
-}
-
 // ------------------------
 // MarlinHAL Class
 // ------------------------
@@ -81,7 +62,9 @@ uint8_t MarlinHAL::get_reset_source() {
   return 0;
 }
 
+// ------------------------
 // ADC
+// ------------------------
 
 void MarlinHAL::adc_init() {
   analog_init();
@@ -102,4 +85,23 @@ void MarlinHAL::adc_start(const pin_t pin) {
 
 uint16_t MarlinHAL::adc_value() { return ADC0_RA; }
 
+// ------------------------
+// Free Memory Accessor
+// ------------------------
+
+extern "C" {
+  extern char __bss_end;
+  extern char __heap_start;
+  extern void* __brkval;
+
+  int freeMemory() {
+    int free_memory;
+    if ((int)__brkval == 0)
+      free_memory = ((int)&free_memory) - ((int)&__bss_end);
+    else
+      free_memory = ((int)&free_memory) - ((int)__brkval);
+    return free_memory;
+  }
+}
+
 #endif // __MK20DX256__
diff --git a/Marlin/src/HAL/TEENSY35_36/HAL.cpp b/Marlin/src/HAL/TEENSY35_36/HAL.cpp
index 54a5ad3855..5fbb49fd92 100644
--- a/Marlin/src/HAL/TEENSY35_36/HAL.cpp
+++ b/Marlin/src/HAL/TEENSY35_36/HAL.cpp
@@ -43,33 +43,12 @@
 
 USBSerialType USBSerial(false, SerialUSB);
 
-// ------------------------
-// Class Utilities
-// ------------------------
-
-extern "C" {
-  extern char __bss_end;
-  extern char __heap_start;
-  extern void* __brkval;
-
-  int freeMemory() {
-    int free_memory;
-    if ((int)__brkval == 0)
-      free_memory = ((int)&free_memory) - ((int)&__bss_end);
-    else
-      free_memory = ((int)&free_memory) - ((int)__brkval);
-    return free_memory;
-  }
-}
-
 // ------------------------
 // MarlinHAL Class
 // ------------------------
 
 void MarlinHAL::reboot() { _reboot_Teensyduino_(); }
 
-// Reset
-
 uint8_t MarlinHAL::get_reset_source() {
   switch (RCM_SRS0) {
     case 128: return RST_POWER_ON; break;
@@ -82,7 +61,9 @@ uint8_t MarlinHAL::get_reset_source() {
   return 0;
 }
 
+// ------------------------
 // ADC
+// ------------------------
 
 int8_t MarlinHAL::adc_select;
 
@@ -131,4 +112,23 @@ uint16_t MarlinHAL::adc_value() {
   return 0;
 }
 
+// ------------------------
+// Free Memory Accessor
+// ------------------------
+
+extern "C" {
+  extern char __bss_end;
+  extern char __heap_start;
+  extern void* __brkval;
+
+  int freeMemory() {
+    int free_memory;
+    if ((int)__brkval == 0)
+      free_memory = ((int)&free_memory) - ((int)&__bss_end);
+    else
+      free_memory = ((int)&free_memory) - ((int)__brkval);
+    return free_memory;
+  }
+}
+
 #endif // __MK64FX512__ || __MK66FX1M0__
diff --git a/Marlin/src/HAL/TEENSY35_36/HAL.h b/Marlin/src/HAL/TEENSY35_36/HAL.h
index c45f2aa493..84f071d73d 100644
--- a/Marlin/src/HAL/TEENSY35_36/HAL.h
+++ b/Marlin/src/HAL/TEENSY35_36/HAL.h
@@ -118,7 +118,7 @@ typedef int8_t pin_t;
 #define PARSED_PIN_INDEX(code, dval) parser.intval(code, dval)
 
 // ------------------------
-// Class Utilities
+// Free Memory Accessor
 // ------------------------
 
 #pragma GCC diagnostic push
diff --git a/Marlin/src/HAL/TEENSY40_41/HAL.cpp b/Marlin/src/HAL/TEENSY40_41/HAL.cpp
index 68bd38f72f..4b9c55a2ca 100644
--- a/Marlin/src/HAL/TEENSY40_41/HAL.cpp
+++ b/Marlin/src/HAL/TEENSY40_41/HAL.cpp
@@ -44,25 +44,6 @@
 #endif
 USBSerialType USBSerial(false, SerialUSB);
 
-// ------------------------
-// Class Utilities
-// ------------------------
-
-#define __bss_end _ebss
-
-extern "C" {
-  extern char __bss_end;
-  extern char __heap_start;
-  extern void* __brkval;
-
-  // Doesn't work on Teensy 4.x
-  uint32_t freeMemory() {
-    uint32_t free_memory;
-    free_memory = ((uint32_t)&free_memory) - (((uint32_t)__brkval) ?: ((uint32_t)&__bss_end));
-    return free_memory;
-  }
-}
-
 // ------------------------
 // FastIO
 // ------------------------
@@ -97,7 +78,9 @@ void MarlinHAL::clear_reset_source() {
   SRC_SRSR = reset_source;
 }
 
+// ------------------------
 // ADC
+// ------------------------
 
 int8_t MarlinHAL::adc_select;
 
@@ -180,4 +163,23 @@ uint16_t MarlinHAL::adc_value() {
   return 0;
 }
 
+// ------------------------
+// Free Memory Accessor
+// ------------------------
+
+#define __bss_end _ebss
+
+extern "C" {
+  extern char __bss_end;
+  extern char __heap_start;
+  extern void* __brkval;
+
+  // Doesn't work on Teensy 4.x
+  uint32_t freeMemory() {
+    uint32_t free_memory;
+    free_memory = ((uint32_t)&free_memory) - (((uint32_t)__brkval) ?: ((uint32_t)&__bss_end));
+    return free_memory;
+  }
+}
+
 #endif // __IMXRT1062__
diff --git a/Marlin/src/HAL/TEENSY40_41/HAL.h b/Marlin/src/HAL/TEENSY40_41/HAL.h
index ea874da2fa..0476a9809d 100644
--- a/Marlin/src/HAL/TEENSY40_41/HAL.h
+++ b/Marlin/src/HAL/TEENSY40_41/HAL.h
@@ -140,7 +140,7 @@ typedef int8_t pin_t;
 bool is_output(pin_t pin);
 
 // ------------------------
-// Class Utilities
+// Free Memory Accessor
 // ------------------------
 
 #pragma GCC diagnostic push
diff --git a/Marlin/src/inc/MarlinConfig.h b/Marlin/src/inc/MarlinConfig.h
index 505a0682eb..8fdb4b9bae 100644
--- a/Marlin/src/inc/MarlinConfig.h
+++ b/Marlin/src/inc/MarlinConfig.h
@@ -29,7 +29,6 @@
 
 #ifndef __MARLIN_DEPS__
   #include "../HAL/HAL.h"
-  extern MarlinHAL hal;
 #endif
 
 #include "../pins/pins.h"