diff --git a/Marlin/src/gcode/config/M200-M205.cpp b/Marlin/src/gcode/config/M200-M205.cpp
index f806fd19d1..08a2b1560b 100644
--- a/Marlin/src/gcode/config/M200-M205.cpp
+++ b/Marlin/src/gcode/config/M200-M205.cpp
@@ -61,7 +61,7 @@ void GcodeSuite::M201() {
 
   LOOP_XYZE(i) {
     if (parser.seen(axis_codes[i])) {
-      const uint8_t a = (i == E_AXIS ? E_AXIS_N(target_extruder) : i);
+      const uint8_t a = (i == uint8_t(E_AXIS) ? E_AXIS_N(target_extruder) : i);
       planner.settings.max_acceleration_mm_per_s2[a] = parser.value_axis_units((AxisEnum)a);
     }
   }
diff --git a/Marlin/src/lcd/HD44780/lcdprint_hd44780.cpp b/Marlin/src/lcd/HD44780/lcdprint_hd44780.cpp
index 38e06ec96a..f888dc48e1 100644
--- a/Marlin/src/lcd/HD44780/lcdprint_hd44780.cpp
+++ b/Marlin/src/lcd/HD44780/lcdprint_hd44780.cpp
@@ -866,11 +866,11 @@ static const hd44780_charmap_t g_hd44780_charmap_common[] PROGMEM = {
 };
 
 /* return v1 - v2 */
-static int hd44780_charmap_compare(hd44780_charmap_t * v1, hd44780_charmap_t * v2) {
+static int hd44780_charmap_compare(const hd44780_charmap_t * const v1, const hd44780_charmap_t * const v2) {
   return (v1->uchar < v2->uchar) ? -1 : (v1->uchar > v2->uchar) ? 1 : 0;
 }
 
-static int pf_bsearch_cb_comp_hd4map_pgm(void *userdata, size_t idx, void * data_pin) {
+static int pf_bsearch_cb_comp_hd4map_pgm(void *userdata, const size_t idx, const void * const data_pin) {
   hd44780_charmap_t localval;
   hd44780_charmap_t *p_hd44780_charmap = (hd44780_charmap_t *)userdata;
   memcpy_P(&localval, p_hd44780_charmap + idx, sizeof(localval));
@@ -883,7 +883,7 @@ void lcd_put_int(const int i) { lcd.print(i); }
 
 // return < 0 on error
 // return the advanced cols
-int lcd_put_wchar_max(wchar_t c, pixel_len_t max_length) {
+int lcd_put_wchar_max(const wchar_t c, pixel_len_t max_length) {
 
   // find the HD44780 internal ROM first
   int ret;
@@ -938,7 +938,7 @@ int lcd_put_wchar_max(wchar_t c, pixel_len_t max_length) {
  *
  * Draw a UTF-8 string
  */
-static int lcd_put_u8str_max_cb(const char * utf8_str, uint8_t (*cb_read_byte)(uint8_t * str), pixel_len_t max_length) {
+static int lcd_put_u8str_max_cb(const char * const utf8_str, uint8_t (*cb_read_byte)(uint8_t * str), pixel_len_t max_length) {
   pixel_len_t ret = 0;
   uint8_t *p = (uint8_t *)utf8_str;
   while (ret < max_length) {
@@ -950,17 +950,17 @@ static int lcd_put_u8str_max_cb(const char * utf8_str, uint8_t (*cb_read_byte)(u
   return (int)ret;
 }
 
-int lcd_put_u8str_max(const char * utf8_str, pixel_len_t max_length) {
+int lcd_put_u8str_max(const char * const utf8_str, pixel_len_t max_length) {
   return lcd_put_u8str_max_cb(utf8_str, read_byte_ram, max_length);
 }
 
-int lcd_put_u8str_max_P(PGM_P utf8_str_P, pixel_len_t max_length) {
+int lcd_put_u8str_max_P(PGM_P const utf8_str_P, pixel_len_t max_length) {
   return lcd_put_u8str_max_cb(utf8_str_P, read_byte_rom, max_length);
 }
 
 #if ENABLED(DEBUG_LCDPRINT)
 
-  int test_hd44780_charmap(hd44780_charmap_t *data, size_t size, char *name, char flg_show_contents) {
+  int test_hd44780_charmap(hd44780_charmap_t *data, const size_t size, const char * const name, const bool flg_show_contents) {
     int ret;
     size_t idx = 0;
     hd44780_charmap_t preval = {0, 0, 0};
diff --git a/Marlin/src/lcd/dogm/lcdprint_u8g.cpp b/Marlin/src/lcd/dogm/lcdprint_u8g.cpp
index d46eb85903..78804f3a9a 100644
--- a/Marlin/src/lcd/dogm/lcdprint_u8g.cpp
+++ b/Marlin/src/lcd/dogm/lcdprint_u8g.cpp
@@ -28,7 +28,7 @@ void lcd_put_int(const int i) { u8g.print(i); }
 
 // return < 0 on error
 // return the advanced pixels
-int lcd_put_wchar_max(wchar_t c, pixel_len_t max_length) {
+int lcd_put_wchar_max(const wchar_t c, pixel_len_t max_length) {
   if (c < 256) {
     u8g.print((char)c);
     return u8g_GetFontBBXWidth(u8g.getU8g());
@@ -41,7 +41,7 @@ int lcd_put_wchar_max(wchar_t c, pixel_len_t max_length) {
   return ret;
 }
 
-int lcd_put_u8str_max(const char * utf8_str, pixel_len_t max_length) {
+int lcd_put_u8str_max(const char * const utf8_str, pixel_len_t max_length) {
   unsigned int x = u8g.getPrintCol(),
                y = u8g.getPrintRow(),
                ret = uxg_DrawUtf8Str(u8g.getU8g(), x, y, utf8_str, max_length);
@@ -49,7 +49,7 @@ int lcd_put_u8str_max(const char * utf8_str, pixel_len_t max_length) {
   return ret;
 }
 
-int lcd_put_u8str_max_P(PGM_P utf8_str_P, pixel_len_t max_length) {
+int lcd_put_u8str_max_P(PGM_P const utf8_str_P, pixel_len_t max_length) {
   unsigned int x = u8g.getPrintCol(),
                y = u8g.getPrintRow(),
                ret = uxg_DrawUtf8StrP(u8g.getU8g(), x, y, utf8_str_P, max_length);
diff --git a/Marlin/src/lcd/dogm/u8g_fontutf8.cpp b/Marlin/src/lcd/dogm/u8g_fontutf8.cpp
index 890cd4217c..80422e9341 100644
--- a/Marlin/src/lcd/dogm/u8g_fontutf8.cpp
+++ b/Marlin/src/lcd/dogm/u8g_fontutf8.cpp
@@ -42,7 +42,7 @@ static int fontinfo_compare(uxg_fontinfo_t * v1, uxg_fontinfo_t * v2) {
 }
 
 /*"data_list[idx] - *data_pin"*/
-static int pf_bsearch_cb_comp_fntifo_pgm (void *userdata, size_t idx, void *data_pin) {
+static int pf_bsearch_cb_comp_fntifo_pgm(void *userdata, const size_t idx, void *data_pin) {
   uxg_fontinfo_t *fntinfo = (uxg_fontinfo_t*)userdata;
   uxg_fontinfo_t localval;
   memcpy_P(&localval, fntinfo + idx, sizeof(localval));
@@ -103,7 +103,7 @@ static void fontgroup_drawwchar(font_group_t *group, const font_t *fnt_default,
  *
  * Get the screen pixel width of a ROM UTF-8 string
  */
-static void fontgroup_drawstring(font_group_t *group, const font_t *fnt_default, const char *utf8_msg, read_byte_cb_t cb_read_byte, void * userdata, fontgroup_cb_draw_t cb_draw_ram) {
+static void fontgroup_drawstring(font_group_t *group, const font_t *fnt_default, const char * const utf8_msg, read_byte_cb_t cb_read_byte, void * userdata, fontgroup_cb_draw_t cb_draw_ram) {
   uint8_t *p = (uint8_t*)utf8_msg;
   for (;;) {
     wchar_t val = 0;
@@ -196,7 +196,7 @@ unsigned int uxg_DrawWchar(u8g_t *pu8g, unsigned int x, unsigned int y, wchar_t
  *
  * Draw a UTF-8 string at the specified position
  */
-unsigned int uxg_DrawUtf8Str(u8g_t *pu8g, unsigned int x, unsigned int y, const char *utf8_msg, pixel_len_t max_width) {
+unsigned int uxg_DrawUtf8Str(u8g_t *pu8g, unsigned int x, unsigned int y, const char * const utf8_msg, pixel_len_t max_width) {
   struct _uxg_drawu8_data_t data;
   font_group_t *group = &g_fontgroup_root;
   const font_t *fnt_default = uxg_GetFont(pu8g);
@@ -230,7 +230,7 @@ unsigned int uxg_DrawUtf8Str(u8g_t *pu8g, unsigned int x, unsigned int y, const
  *
  * Draw a ROM UTF-8 string at the specified position
  */
-unsigned int uxg_DrawUtf8StrP(u8g_t *pu8g, unsigned int x, unsigned int y, PGM_P utf8_msg, pixel_len_t max_width) {
+unsigned int uxg_DrawUtf8StrP(u8g_t *pu8g, unsigned int x, unsigned int y, PGM_P const utf8_msg, pixel_len_t max_width) {
   struct _uxg_drawu8_data_t data;
   font_group_t *group = &g_fontgroup_root;
   const font_t *fnt_default = uxg_GetFont(pu8g);
@@ -273,7 +273,7 @@ static int fontgroup_cb_draw_u8gstrlen(void *userdata, const font_t *fnt_current
  *
  * Get the screen pixel width of a UTF-8 string
  */
-int uxg_GetUtf8StrPixelWidth(u8g_t *pu8g, const char *utf8_msg) {
+int uxg_GetUtf8StrPixelWidth(u8g_t *pu8g, const char * const utf8_msg) {
   struct _uxg_drawu8_data_t data;
   font_group_t *group = &g_fontgroup_root;
   const font_t *fnt_default = uxg_GetFont(pu8g);
@@ -299,7 +299,7 @@ int uxg_GetUtf8StrPixelWidth(u8g_t *pu8g, const char *utf8_msg) {
  *
  * Get the screen pixel width of a ROM UTF-8 string
  */
-int uxg_GetUtf8StrPixelWidthP(u8g_t *pu8g, PGM_P utf8_msg) {
+int uxg_GetUtf8StrPixelWidthP(u8g_t *pu8g, PGM_P const utf8_msg) {
   struct _uxg_drawu8_data_t data;
   font_group_t *group = &g_fontgroup_root;
   const font_t *fnt_default = uxg_GetFont(pu8g);
diff --git a/Marlin/src/lcd/dogm/u8g_fontutf8.h b/Marlin/src/lcd/dogm/u8g_fontutf8.h
index 34e365cf95..3e7de24b75 100644
--- a/Marlin/src/lcd/dogm/u8g_fontutf8.h
+++ b/Marlin/src/lcd/dogm/u8g_fontutf8.h
@@ -28,10 +28,10 @@ int uxg_SetUtf8Fonts(const uxg_fontinfo_t * fntinfo, int number); // fntinfo is
 
 unsigned int uxg_DrawWchar(u8g_t *pu8g, unsigned int x, unsigned int y, wchar_t ch, pixel_len_t max_length);
 
-unsigned int uxg_DrawUtf8Str(u8g_t *pu8g, unsigned int x, unsigned int y, const char *utf8_msg, pixel_len_t max_length);
-unsigned int uxg_DrawUtf8StrP(u8g_t *pu8g, unsigned int x, unsigned int y, PGM_P utf8_msg, pixel_len_t max_length);
+unsigned int uxg_DrawUtf8Str(u8g_t *pu8g, unsigned int x, unsigned int y, const char * const utf8_msg, pixel_len_t max_length);
+unsigned int uxg_DrawUtf8StrP(u8g_t *pu8g, unsigned int x, unsigned int y, PGM_P const utf8_msg, pixel_len_t max_length);
 
-int uxg_GetUtf8StrPixelWidth(u8g_t *pu8g, const char *utf8_msg);
-int uxg_GetUtf8StrPixelWidthP(u8g_t *pu8g, PGM_P utf8_msg);
+int uxg_GetUtf8StrPixelWidth(u8g_t *pu8g, const char * const utf8_msg);
+int uxg_GetUtf8StrPixelWidthP(u8g_t *pu8g, PGM_P const utf8_msg);
 
 #define uxg_GetFont(puxg) ((puxg)->font)
diff --git a/Marlin/src/lcd/lcdprint.h b/Marlin/src/lcd/lcdprint.h
index 59cd546855..594e159b6e 100644
--- a/Marlin/src/lcd/lcdprint.h
+++ b/Marlin/src/lcd/lcdprint.h
@@ -22,7 +22,7 @@
 
 int lcd_glyph_height(void);
 
-int lcd_put_wchar_max(wchar_t c, pixel_len_t max_length);
+int lcd_put_wchar_max(const wchar_t c, pixel_len_t max_length);
 
 /**
  * @brief Draw a UTF-8 string
@@ -34,7 +34,7 @@ int lcd_put_wchar_max(wchar_t c, pixel_len_t max_length);
  *
  * Draw a UTF-8 string
  */
-int lcd_put_u8str_max(const char * utf8_str, pixel_len_t max_length);
+int lcd_put_u8str_max(const char * const utf8_str, pixel_len_t max_length);
 
 /**
  * @brief Draw a ROM UTF-8 string
@@ -46,14 +46,14 @@ int lcd_put_u8str_max(const char * utf8_str, pixel_len_t max_length);
  *
  * Draw a ROM UTF-8 string
  */
-int lcd_put_u8str_max_P(PGM_P utf8_str_P, pixel_len_t max_length);
+int lcd_put_u8str_max_P(PGM_P const utf8_str_P, pixel_len_t max_length);
 
 void lcd_moveto(const uint8_t col, const uint8_t row);
 
 void lcd_put_int(const int i);
 
-inline int lcd_put_u8str_P(PGM_P str) { return lcd_put_u8str_max_P(str, PIXEL_LEN_NOLIMIT); }
+inline int lcd_put_u8str_P(PGM_P const str) { return lcd_put_u8str_max_P(str, PIXEL_LEN_NOLIMIT); }
 
-inline int lcd_put_u8str(const char* str) { return lcd_put_u8str_max(str, PIXEL_LEN_NOLIMIT); }
+inline int lcd_put_u8str(const char * const str) { return lcd_put_u8str_max(str, PIXEL_LEN_NOLIMIT); }
 
 inline int lcd_put_wchar(const wchar_t c) { return lcd_put_wchar_max(c, PIXEL_LEN_NOLIMIT); }
diff --git a/Marlin/src/lcd/ultralcd.cpp b/Marlin/src/lcd/ultralcd.cpp
index 8cecbd9182..8d11dabaec 100644
--- a/Marlin/src/lcd/ultralcd.cpp
+++ b/Marlin/src/lcd/ultralcd.cpp
@@ -130,7 +130,7 @@ millis_t next_button_update_ms;
       uint8_t MarlinUI::filename_scroll_pos, MarlinUI::filename_scroll_max;
     #endif
 
-    const char * const MarlinUI::scrolled_filename(CardReader &theCard, const uint8_t maxlen, uint8_t hash, const bool doScroll) {
+    const char * MarlinUI::scrolled_filename(CardReader &theCard, const uint8_t maxlen, uint8_t hash, const bool doScroll) {
       const char *outstr = theCard.longest_filename();
       if (theCard.longFilename[0]) {
         #if ENABLED(SCROLL_LONG_FILENAMES)
diff --git a/Marlin/src/lcd/ultralcd.h b/Marlin/src/lcd/ultralcd.h
index 9465dc6161..61524a082b 100644
--- a/Marlin/src/lcd/ultralcd.h
+++ b/Marlin/src/lcd/ultralcd.h
@@ -380,7 +380,7 @@ public:
       #if ENABLED(SCROLL_LONG_FILENAMES)
         static uint8_t filename_scroll_pos, filename_scroll_max;
       #endif
-      static const char * const scrolled_filename(CardReader &theCard, const uint8_t maxlen, uint8_t hash, const bool doScroll);
+      static const char * scrolled_filename(CardReader &theCard, const uint8_t maxlen, uint8_t hash, const bool doScroll);
     #endif
 
     #if IS_KINEMATIC