diff --git a/src/core/features/course/components/course-format/course-format.ts b/src/core/features/course/components/course-format/course-format.ts
index d9e925eb9..3c432a9c1 100644
--- a/src/core/features/course/components/course-format/course-format.ts
+++ b/src/core/features/course/components/course-format/course-format.ts
@@ -51,7 +51,6 @@ import { CoreCourseCourseIndexTourComponent } from '../course-index-tour/course-
 import { CoreDom } from '@singletons/dom';
 import { CoreUserTourDirectiveOptions } from '@directives/user-tour';
 import { CoreAnalytics, CoreAnalyticsEventType } from '@services/analytics';
-import { CorePlatform } from '@services/platform';
 import { CoreBlockSideBlocksComponent } from '@features/block/components/side-blocks/side-blocks';
 
 /**
@@ -96,7 +95,7 @@ export class CoreCourseFormatComponent implements OnInit, OnChanges, OnDestroy {
         id: 'course-index',
         component: CoreCourseCourseIndexTourComponent,
         side: CoreUserToursSide.Top,
-        alignment: CorePlatform.isRTL ? CoreUserToursAlignment.Start : CoreUserToursAlignment.End,
+        alignment: CoreUserToursAlignment.End,
         getFocusedElement: nativeButton => {
             const innerButton = Array.from(nativeButton.shadowRoot?.children ?? []).find(child => child.tagName === 'BUTTON');
 
diff --git a/src/theme/helpers/ionic.functions.string.scss b/src/theme/helpers/ionic.functions.string.scss
index 34a01c114..6b411ef28 100644
--- a/src/theme/helpers/ionic.functions.string.scss
+++ b/src/theme/helpers/ionic.functions.string.scss
@@ -92,23 +92,7 @@
 
 // Add Root Selector
 // --------------------------------------------------------------------------------
-// Adds a root selector using host-context based on the selector passed
-//
-// Examples
-// --------------------------------------------------------------------------------
-// @include add-root-selector("[dir=rtl]", ":host")
-// --> :host-context([dir=rtl])
-//
-// @include add-root-selector("[dir=rtl]", ":host(.fixed)")
-// --> :host-context([dir=rtl]):host(.fixed)
-// --> :host-context([dir=rtl]).fixed
-//
-// @include add-root-selector("[dir=rtl]", ":host(.tab-layout-icon-hide) ::slotted(ion-badge)")
-// --> :host-context([dir=rtl]).tab-layout-icon-hide ::slotted(ion-badge)
-//
-// @include add-root-selector("[dir=rtl]", ".shadow")
-// --> [dir=rtl] .shadow
-// --> :host-context([dir=rtl]) .shadow
+// Adds a root selector using host based on the selector passed
 // --------------------------------------------------------------------------------
 
 @function add-root-selector($root, $addHostSelector) {
@@ -118,8 +102,13 @@
 
   @each $selector in $selectors {
     // If the selector contains :host( it means it is targeting a class on the host
-    // element so we need to change how we target it
+    // element so we need to change how we target it:
+    // @include add-root-selector(":host(.fixed)", "[dir=rtl]")
+    // --> :host-context([dir=rtl]):host(.fixed)
+    // --> :host-context([dir=rtl]).fixed
     @if str-contains($selector, ":host(") {
+      // @include add-root-selector(":host(.fixed)", "[dir=rtl]")
+      // --> :host-context([dir=rtl]):host(.fixed)
       $shadow-element: str-replace($selector, ":host(", ":host-context(#{$addHostSelector}):host(");
       $list: append($list, $shadow-element, comma);
 
@@ -130,27 +119,63 @@
         @if str-contains($element, ":host(") {
           $scoped-element: $element;
 
-          @if str-contains($element, "))") {
-            $scoped-element: str-replace($scoped-element, "))", ")");
-          } @else {
-            $scoped-element: str-replace($scoped-element, ")", "");
-          }
-          $scoped-element: str-replace($scoped-element, ":host(", ":host-context(#{$addHostSelector})");
+          // Replace the :host( and ) so all we have left is the class
+          // inside of it:
+          // :host(.fixed) -> .fixed
+          $scoped-element: str-replace($scoped-element, ")", "");
+          $scoped-element: str-replace($scoped-element, ":host(", "");
 
+          // Add the class back inside of host with the rtl selector:
+          // .fixed -> :host-context([dir=rtl]).fixed
+          $scoped-element: str-replace($scoped-element, $scoped-element, ":host-context(#{$addHostSelector})#{$scoped-element}");
+
+          // @include add-root-selector(":host(.fixed)", "[dir=rtl]")
+          // --> :host-context([dir=rtl]).fixed
           $new-element: append($new-element, $scoped-element, space);
         } @else {
+          // Add back any selectors that followed the host after transforming the
+          // first selector:
+          // :host(.fixed) ::slotted(ion-icon)
+          // --> :host-context([dir=rtl]):host(.fixed) ::slotted(ion-icon)
+          // --> :host-context([dir=rtl]).fixed ::slotted(ion-icon)
           $new-element: append($new-element, $element, space);
         }
       }
 
       $list: append($list, $new-element, comma);
-    // If the selector contains :host it means it is targeting just the host
+    // If the selector contains :host without a parantheses
+    // it means it is targeting just the host
     // element so we can change it to look for host-context
+    // @include add-root-selector(":host", "[dir=rtl]")
+    // --> :host-context([dir=rtl])
+    // --> :host:dir(rtl)
     } @else if str-contains($selector, ":host") {
-      $shadow-element: str-replace($selector, ":host", ":host-context(#{$addHostSelector})");
-      $list: append($list, $shadow-element, comma);
-      // If the selector does not contain host at all it is either a shadow
-      // or normal element so append both the dir check and host-context
+      $new-element: ();
+      $elements: str-split($selector, " ");
+
+      @each $element in $elements {
+        @if str-contains($element, ":host") {
+          // Replace the :host with the addHostSelector:
+          // :host -> :host-context([dir=rtl])
+          $updated-element: str-replace($element, ":host", ":host-context(#{$addHostSelector})");
+
+          // Add the final selector after all transformations:
+          // :host -> :host-context([dir=rtl])
+          $new-element: append($new-element, $updated-element, space);
+        } @else {
+          // Add back any selectors that followed the host after transforming the
+          // first selector:
+          // :host ::slotted(ion-icon) -> :host-context([dir=rtl]) ::slotted(ion-icon)
+          $new-element: append($new-element, $element, space);
+        }
+      }
+
+      $list: append($list, $new-element, comma);
+    // If the selector does not contain host at all it is either a shadow
+    // or normal element so append both the addHostSelector and host-context
+    // @include add-root-selector("ion-component", "[dir=rtl]")
+    // --> :host-context([dir=rtl]) ion-component
+    // --> [dir=rtl] ion-component
     } @else {
       $list: append($list, "#{$addHostSelector} #{$selector}", comma);
       $list: append($list, ":host-context(#{$addHostSelector}) #{$selector}", comma);
diff --git a/src/theme/helpers/ionic.mixins.scss b/src/theme/helpers/ionic.mixins.scss
index f212ad5f7..d74f2011c 100644
--- a/src/theme/helpers/ionic.mixins.scss
+++ b/src/theme/helpers/ionic.mixins.scss
@@ -201,9 +201,67 @@
 @mixin rtl() {
   $root: #{&};
 
-  @at-root #{add-root-selector($root, "[dir=rtl]")} {
-    @content;
+  $rootSplit: str-split($root, ",");
+  $selectors: #{add-root-selector($root, "[dir=rtl]")};
+  $selectorsSplit: str-split($selectors, ",");
+
+  $hostContextSelectors: ();
+  $restSelectors: ();
+  $dirSelectors: ();
+
+  // Selectors must be split into individual selectors in case the browser
+  // doesn't support a specific selector.
+  // For example, Firefox and Safari doesn't support `:host-context()`.
+  // If an invalid selector is used, then the entire group of selectors
+  // will be ignored.
+  // @link https://www.w3.org/TR/selectors-3/#grouping
+  @each $selector in $selectorsSplit {
+    // Group the selectors back into a single selector to optimize the output.
+    @if str-index($selector, ":host-context") {
+      $hostContextSelectors: append($hostContextSelectors, $selector, comma);
+    } @else {
+      // Group the selectors back into a single selector to optimize the output.
+      $restSelectors: append($restSelectors, $selector, comma);
+    }
   }
+
+  // Supported by Chrome.
+  @if length($hostContextSelectors) > 0 {
+    @at-root #{$hostContextSelectors} {
+      @content;
+    }
+  }
+
+  // Supported by all browsers.
+  @if length($restSelectors) > 0 {
+    @at-root #{$restSelectors} {
+      @content;
+    }
+  }
+
+  // If browser can support `:dir()`, then add the `:dir()` selectors.
+  // @supports selector(:dir(rtl)) { // @ IMPOTANT NOTE: This has been removed because selector function is not supported in current SCSS
+  // Adding :dir() in case the browser doesn't support `:host-context()` and does support `:dir()`.
+  // `:host-context()` is added:
+  // - through the `add-root-selector()` function.
+  // - first so that it takes precedence over `:dir()`.
+  // For example,
+  // - Firefox doesn't support `:host-context()`, but does support `:dir()`.
+  // - Safari doesn't support `:host-context()`, but Safari 16.4+ supports `:dir()`
+  // @link https://webkit.org/blog/13966/webkit-features-in-safari-16-4/
+  @each $selector in $rootSplit {
+    $dirSelector: "#{$selector}:dir(rtl)";
+    // Group the selectors back into a single selector to optimize the output.
+    $dirSelectors: append($dirSelectors, $dirSelector, comma);
+  }
+
+  // Supported by Firefox.
+  @if length($dirSelectors) > 0 {
+    @at-root #{$dirSelectors} {
+      @content;
+    }
+  }
+  //}
 }
 
 @mixin ltr() {
@@ -249,26 +307,10 @@
     #{$prop}-right: $end;
 
   } @else {
-    #{$prop}-left: $start;
-    #{$prop}-right: $end;
-
-    @at-root {
-      @supports ((margin-inline-start: 0) or (-webkit-margin-start: 0)) {
-        & {
-          @if $start != null {
-            #{$prop}-left: unset;
-          }
-          @if $end != null {
-            #{$prop}-right: unset;
-          }
-
-          -webkit-#{$prop}-start: $start;
-          #{$prop}-inline-start: $start;
-          -webkit-#{$prop}-end: $end;
-          #{$prop}-inline-end: $end;
-        }
-      }
-    }
+    -webkit-#{$prop}-start: $start;
+    #{$prop}-inline-start: $start;
+    -webkit-#{$prop}-end: $end;
+    #{$prop}-inline-end: $end;
   }
 }
 
@@ -333,16 +375,32 @@
       right: $end;
     }
   } @else {
-    @include ltr() {
-      left: $start;
-      right: $end;
+    @at-root {
+      @supports (inset-inline-start: 0) {
+        & {
+          inset-inline-start: $start;
+          inset-inline-end: $end;
+        }
+      }
     }
-    @include rtl() {
-      left: unset;
-      right: unset;
 
-      left: $end;
-      right: $start;
+    // TODO FW-3766
+    @at-root {
+      @supports not (inset-inline-start: 0) {
+        & {
+          @include ltr() {
+            left: $start;
+            right: $end;
+          }
+          @include rtl() {
+            left: unset;
+            right: unset;
+
+            left: $end;
+            right: $start;
+          }
+        }
+      }
     }
   }
 }
diff --git a/src/theme/theme.base.scss b/src/theme/theme.base.scss
index 88ba3383f..5ebfcbfd0 100644
--- a/src/theme/theme.base.scss
+++ b/src/theme/theme.base.scss
@@ -704,6 +704,8 @@ body.core-iframe-fullscreen ion-router-outlet {
     --ion-safe-area-right: 0px;
 
     .modal-wrapper {
+        @include margin-horizontal(var(--modal-lateral-margin), null);
+
         position: absolute;
         @include position(0 !important, 0 !important, 0 !important, unset !important);
         display: block;
@@ -722,14 +724,6 @@ body.core-iframe-fullscreen ion-router-outlet {
     }
 }
 
-html:not([dir="rtl"]) {
-    .core-modal-lateral {
-        .modal-wrapper {
-            @include margin-horizontal(var(--modal-lateral-margin), null);
-        }
-    }
-}
-
 .core-modal-transparent-no-filter {
     @extend .core-modal-transparent;
     ion-backdrop {
@@ -1340,6 +1334,25 @@ ion-fab[core-fab] {
     }
 }
 
+// The following 4 selectors can probably be removed after Ionic migration to 7+
+ion-fab.fab-horizontal-start {
+    left: calc(10px + var(--ion-safe-area-right, 0px));
+}
+
+[dir=rtl] ion-fab.fab-horizontal-start {
+    right: calc(10px + var(--ion-safe-area-right, 0px));
+    left: unset
+}
+
+ion-fab.fab-horizontal-end {
+    right: calc(10px + var(--ion-safe-area-right, 0px));
+}
+
+[dir=rtl] ion-fab.fab-horizontal-end {
+    left: calc(10px + var(--ion-safe-area-right, 0px));
+    right: unset
+}
+
 ion-content.has-collapsible-footer ion-fab {
     bottom: calc(var(--core-collapsible-footer-height, 0px) + 10px);
     @include core-transition(all, 200ms);