Add this to your theme’s functions.php file. Read more: https://sushyant.com/wordpress/prevent-users-from-changing-email-address

Prevent Users From Changing E-mail Address

class DisableEmailChange
{


    function __construct()
    {


        add_action('admin_footer', array($this, 'disable_userprofile_fields'));


    }


    function disable_userprofile_fields()
    {

        global $pagenow;

        if ($pagenow == 'profile.php' && !current_user_can( 'manage_options' )) {

            ?>
            <script>
                jQuery(document).ready(function ($) {
                    if ($('input[name=email]').length) {
                        $('input[name=email]').attr("disabled", "disabled");
                    }

                });
            </script>
        <?php
        }
    }

} // End Class

$DisableEmailChange = new DisableEmailChange();