Get all user meta_keys and then group users by matching values

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