start components

scss/forms/_form-check.scss

@@ -173,3 +173,12 @@
     }
   }
 }
+
+@if $enable-dark-mode {
+  [data-theme="dark"] {
+    // Use `:not()` to keep from having to override subsequent embedded SVGs
+    .form-switch .form-check-input:not(:checked):not(:focus) {
+      background-image: escape-svg($form-switch-bg-image-dark);
+    }
+  }
+}

scss/forms/_form-select.scss

@@ -69,3 +69,11 @@
   @include font-size($form-select-font-size-lg);
   @include border-radius($form-select-border-radius-lg);
 }
+
+@if $enable-dark-mode {
+  [data-theme="dark"] {
+    .form-select {
+      background-image: escape-svg($form-select-indicator-dark);
+    }
+  }
+}