It would be nice if the system could warn about SELinux forbidding ComfortUpdate. Currently _updatesavailable_error.php contains

    case 'no_server_answer':
        . . .
        $sMessage = gT("It seems that the ComfortUpdate server is not responding. Please try again in few minutes or contact the LimeSurvey team.");

and it could be something like

    case 'no_server_answer':
        . . .
        $check_selinux = array();
        $res = 0;
        exec("getsebool httpd_can_network_connect", $check_selinux, $res);
        if ($res == 0 and explode(" ", $check_selinux[0])[2] == "off")
            $sMessage = gT("It seems that the ComfortUpdate server is not responding, propably because of SELinux restrict connections.");
        else
            $sMessage = gT("It seems that the ComfortUpdate server is not responding. Please try again in few minutes or contact the LimeSurvey team.");