I got the answer after went through WP_User_Query
documentation. Following is the final query:
$args = [
'role__not_in' => 'Administrator',
'meta_key' => 'designation',
'meta_query '=> [
'meta_key' => 'designation'
],
'orderby' => array(
'meta_value'=>'ASC'
)
];
$my_user_query = new WP_User_Query( $args );