It looks like HAS_ONBOARD_SD is obsolete

Marlin/src/HAL/STM32F1/msc_sd.cpp

@@ -25,7 +25,7 @@ USBCompositeSerial MarlinCompositeSerial;
 
 #include "../../inc/MarlinConfig.h"
 
-#ifdef HAS_ONBOARD_SD
+#if SD_CONNECTION_IS(ONBOARD)
 
   #include "onboard_sd.h"
 
@@ -47,7 +47,7 @@ void MSC_SD_init() {
   USBComposite.end();
   USBComposite.clear();
   // Set api and register mass storage
-  #ifdef HAS_ONBOARD_SD
+  #if SD_CONNECTION_IS(ONBOARD)
     uint32_t cardSize;
     if (disk_initialize(0) == RES_OK) {
       if (disk_ioctl(0, GET_SECTOR_COUNT, (void *)(&cardSize)) == RES_OK) {

Marlin/src/HAL/STM32F1/onboard_sd.cpp

@@ -14,13 +14,13 @@
 
 #include "../../inc/MarlinConfig.h"
 
-#ifdef HAS_ONBOARD_SD
+#if SD_CONNECTION_IS(ONBOARD)
 
 #include "onboard_sd.h"
 #include "SPI.h"
 #include "fastio.h"
 
-#ifdef SHARED_SD_CARD
+#if ENABLED(SHARED_SD_CARD)
   #ifndef ON_BOARD_SPI_DEVICE
     #define ON_BOARD_SPI_DEVICE SPI_DEVICE
   #endif
@@ -553,4 +553,4 @@ DRESULT disk_read (
 
 #endif // _DISKIO_IOCTL
 
-#endif // HAS_ONBOARD_SD
+#endif // SD_CONNECTION_IS(ONBOARD)

Marlin/src/inc/Conditionals_post.h

@@ -339,7 +339,7 @@
   #endif
 
   #if DISABLED(SHARED_SD_CARD)
-    #define INIT_SDCARD_ON_BOOT 1
+    #define INIT_SDCARD_ON_BOOT
   #endif
 
   #if PIN_EXISTS(SD_DETECT)

Marlin/src/pins/stm32f1/pins_BTT_SKR_E3_DIP.h

@@ -223,8 +223,6 @@
 //
 // SD Support
 //
-#define HAS_ONBOARD_SD
-
 #ifndef SDCARD_CONNECTION
   #define SDCARD_CONNECTION              ONBOARD
 #endif

Marlin/src/pins/stm32f1/pins_BTT_SKR_MINI_E3.h

@@ -181,8 +181,6 @@
 //
 // SD Support
 //
-#define HAS_ONBOARD_SD
-
 #ifndef SDCARD_CONNECTION
   #define SDCARD_CONNECTION              ONBOARD
 #endif

Marlin/src/pins/stm32f1/pins_BTT_SKR_MINI_V1_1.h

@@ -179,8 +179,7 @@
 //
 
 // By default the onboard SD is enabled.
-// set SDCARD_CONNECTION form 'ONBOARD' to 'LCD' and use an external SD (connected to LCD)
-#define HAS_ONBOARD_SD
+// Change SDCARD_CONNECTION from 'ONBOARD' to 'LCD' for an external (LCD module) SD
 #ifndef SDCARD_CONNECTION
   #define SDCARD_CONNECTION              ONBOARD
 #endif