Adding an axis to a chart can be done independently of the series.

Attaching an axis to a series cannot be done until the series is attached to the chart.

Adding a series to a chart causes it to be rendered. (this may be a problem with qchartview rendering on every change?)

Attaching the axis to the series causes the series to be rendered again.

It is impossible to avoid this flicker because the axis cannot be attached to a series before the series is attached to the chart.

This is a design flaw.

 SEE: QChart::addSeries:

https://github.com/qt/qtcharts/blob/fe003ee4fcaae8ceb877112d63c22bda2e9f06fd/src/charts/qchart.cpp#L273

SEE: QAbstractSeries::attachAxis:

https://github.com/qt/qtcharts/blob/fe003ee4fcaae8ceb877112d63c22bda2e9f06fd/src/charts/qabstractseries.cpp#L382