returns 96, whereas I have 158.338.
In Qt 6.2.3 all is fine with this, you created a new bug in Qt 6.3.0.
[Reg 5.15 -> 6.3] QScreen::physicalSize() and QScreen::physicalDotsPerInch() give wrong results
Improper handling of TILED displays (4K / 5K / 8K etc.) / support for RandR v1.5