Index: src/wp-admin/includes/media.php
===================================================================
--- src/wp-admin/includes/media.php	(revision 58366)
+++ src/wp-admin/includes/media.php	(working copy)
@@ -3267,7 +3267,14 @@
 		'textarea_name' => 'content',
 		'textarea_rows' => 5,
 		'media_buttons' => false,
-		'tinymce'       => false,
+		/**
+		 * Filters the media description for tinymce.
+		 *
+		 * @since 6.6
+		 *
+		 * @param bool Activate TinyMCE in media description field. Default false.
+		 */
+		'tinymce'       => apply_filters( 'activate_tinymce_for_media_description', false ),
 		'quicktags'     => $quicktags_settings,
 	);