There is an observed difference between Qt5 and Qt6 for the returned horizontalAdvance value for the same text element. This becomes apparent for scale values above 100%

See the attached sample project, the returned values depend on the largest scale value of any connected monitors.

In Qt 6.5.x, 108 is returned whenever the scale value is above 100%

In Qt 5.15.x, differing values are returned depending on the scale value.