Index: src/wp-includes/class-wpdb.php
===================================================================
--- src/wp-includes/class-wpdb.php	(revision 53921)
+++ src/wp-includes/class-wpdb.php	(working copy)
@@ -3945,17 +3945,27 @@
 	 * @return bool True when the database feature is supported, false otherwise.
 	 */
 	public function has_cap( $db_cap ) {
-		$version = $this->db_version();
+		$db_version     = $this->db_version();
+		$db_server_info = $this->db_server_info();
 
+		// Account for MariaDB version being prefixed with '5.5.5-' on older PHP versions.
+		if ( '5.5.5' === $db_version && str_contains( $db_server_info, 'MariaDB' )
+			&& PHP_VERSION_ID < 80016 // PHP 8.0.15 or older.
+		) {
+			// Strip the '5.5.5-' prefix and set the version to the correct value.
+			$db_server_info = preg_replace( '/^5\.5\.5-(.*)/', '$1', $db_server_info );
+			$db_version     = preg_replace( '/[^0-9.].*/', '', $db_server_info );
+		}
+
 		switch ( strtolower( $db_cap ) ) {
 			case 'collation':    // @since 2.5.0
 			case 'group_concat': // @since 2.7.0
 			case 'subqueries':   // @since 2.7.0
-				return version_compare( $version, '4.1', '>=' );
+				return version_compare( $db_version, '4.1', '>=' );
 			case 'set_charset':
-				return version_compare( $version, '5.0.7', '>=' );
+				return version_compare( $db_version, '5.0.7', '>=' );
 			case 'utf8mb4':      // @since 4.1.0
-				if ( version_compare( $version, '5.5.3', '<' ) ) {
+				if ( version_compare( $db_version, '5.5.3', '<' ) ) {
 					return false;
 				}
 				if ( $this->use_mysqli ) {
@@ -3975,7 +3985,7 @@
 					return version_compare( $client_version, '5.5.3', '>=' );
 				}
 			case 'utf8mb4_520': // @since 4.6.0
-				return version_compare( $version, '5.6', '>=' );
+				return version_compare( $db_version, '5.6', '>=' );
 			case 'identifier_placeholders': // @since 6.1.0
 				/*
 				 * As of WordPress 6.1, wpdb::prepare() supports identifiers via '%i',
Index: tests/phpunit/tests/db/charset.php
===================================================================
--- tests/phpunit/tests/db/charset.php	(revision 53921)
+++ tests/phpunit/tests/db/charset.php	(working copy)
@@ -47,7 +47,7 @@
 		self::$db_server_info = self::$_wpdb->db_server_info();
 
 		// Account for MariaDB version being prefixed with '5.5.5-' on older PHP versions.
-		if ( str_contains( self::$db_server_info, 'MariaDB' ) && '5.5.5' === self::$db_version
+		if ( '5.5.5' === self::$db_version && str_contains( self::$db_server_info, 'MariaDB' )
 			&& PHP_VERSION_ID < 80016 // PHP 8.0.15 or older.
 		) {
 			// Strip the '5.5.5-' prefix and set the version to the correct value.
@@ -1189,4 +1189,20 @@
 
 		self::$_wpdb->set_charset( self::$_wpdb->dbh );
 	}
+
+	/**
+	 * @ticket 54841
+	 */
+	public function test_mariadb_supports_utf8mb4_520() {
+		global $wpdb;
+
+		// utf8mb4_520 is available in MariaDB since version 10.2.
+		if ( ! str_contains( self::$db_server_info, 'MariaDB' )
+			|| version_compare( self::$db_version, '10.2', '<' )
+		) {
+			$this->markTestSkipped( 'This test requires MariaDB 10.2 or later.' );
+		}
+
+		$this->assertTrue( $wpdb->has_cap( 'utf8mb4_520' ) );
+	}
 }