Eventually came to a solution in case anyone needs it:
function mb_get_user_meta_values( $mb_user_meta_key ) {
if( empty($mb_user_meta_key) )
return;
$mb_get_users = get_users( array( 'meta_key' => $mb_user_meta_key ) );
$mb_user_meta_values = array();
foreach( $mb_get_users as $mb_user ) {
$mb_user_meta_values[] = get_user_meta( $mb_user->ID, $mb_user_meta_key, true );
}
$mb_user_meta_values = array_unique( $mb_user_meta_values );
return $mb_user_meta_values;
}
Then I can loop through the get_users
with the meta_value