Add following code in your theme’s (child theme’s if any) functions.php

add_filter( 'fep_directory_arguments', function( $args ){
    if ( ! empty( $_GET['fep-search'] ) && in_array( $_GET['fep-search'], [ 'Individual', 'Corporate' ] ) ) {
        $args['meta_query'][] = [
            'key' => 'group_type',
            'value' => $_GET['fep-search'],
        ];
        unset( $args['search'] );
    }
    return $args;
});

(untested).

if you search users with Individual or Corporate (case sensitive) then they will be searched with that meta.