How to update/redraw QChart after data is added to QLineSeries?

Appending a value to QLineSeries using the operator << or the append method should repaint the graph. If it does not happen form some reason, you could trying calling the repaint method on the QChartView.

Here is some code that will center the data once it is added with a cap of at most once per second:

// Global or class scope or
qreal max=-10000000000;
qreal min=-max;
qreal *maxp=&max;
qreal *minp=&min;

// Same scope as before
connect(gTask, &GeneticTask::point, this, [=](QPointF pt) {
        if(pt.y()>*maxp) {
            *maxp=pt.y();
        }
        if(pt.y()<*minp) {
            *minp=pt.y();
        }
        *series<<pt;
        quint64 now=QDateTime::currentMSecsSinceEpoch();
        if(now-(*lastp)>1000) {
            qDebug()<<"UPDATE";
            chart->axisX()->setRange(0,series->count());
            chart->axisY()->setRange(*minp,*maxp);

            *lastp=now;
        }
    }
);