The error message "utf8mb4 requires a newer client library" in the WordPress site health check typically indicates that the MySQL client library used by PHP is outdated and doesn't support the utf8mb4 character set.

To resolve this issue, you have a few options:

1. Update MySQL Client Library:

   • Ensure that you have the latest version of the MySQL client library installed on your server. You can update it using your package manager (e.g., apt, yum) or by downloading the latest version from the official MySQL website.

2. Upgrade MySQL Server:

   • If you're running an older version of MySQL, consider upgrading to a newer version that fully supports utf8mb4. This should automatically update the client library as well.

3. Update PHP:

   • Ensure that you're using a PHP version that is compatible with utf8mb4. PHP versions 7.2 and above fully support utf8mb4.

4. Check MySQL Server Configuration:

   • Verify that the MySQL server is configured to use utf8mb4. You can do this by checking the my.cnf or my.ini configuration file.

   • Look for lines like:

     SQL

• • character-set-server=utf8mb4 collation-server=utf8mb4_unicode_ci

• Check Database and Tables:

  • Make sure that your database and its tables are using the utf8mb4 character set. This can be set during the database creation or by modifying existing tables.

  • You can convert existing tables to utf8mb4 using SQL queries.

• Update WordPress:

  • Ensure that you're using the latest version of WordPress. Newer versions are designed to work with utf8mb4.

• Check Database Connection:

  • Verify that your WordPress configuration (usually found in wp-config.php) is correctly set up to connect to the MySQL server.

  • Look for lines like:

    php