Add following code in your theme’s (child theme’s if you are using) functions.php
add_filter( 'fep_locate_template', function( $template, $template_names ) {
if ( in_array( 'view-message.php', $template_names ) ) {
$template = fep_locate_template( 'view-message-legacy.php' );
}
return $template;
}, 10, 2 );