Weird behaviour of QPainter::render() in QT 6.0.0

Good morning to all.
I'm developing a project that needs to create some QR codes. I realized it using a QGraphicsScene, populate it with grahics and text, and then saving any scene in SVG and PDF using a for cycle.

I started using QT6.0.0; I noticed that the graphics elements used to populate the scene were correctly saved. Instead, the text was saved in SVG files, but not saved in PDF files.

After several attempts, I switch the configuration to QT 5.15.2, and all was correctly stored!!

All fine, except that the SVG shows a different text font size for the same scene.

So, there are two suspected bugs:

1. When I save the same scene in SVG and PDF, I obtain a different graphical representation for text;
2. Using QT 6.0.0, saving the scene in SVG is correct; in PDF the system doesn't print text.

I link a project that shows what I say.

Update to a more recent Qt6 version. See also https://bugreports.qt.io/browse/QTBUG-89727

Thank you, Christian. I update my Qt version to 6.1.1 and I fixed the bug concerning missing text.

But the difference between SVG and PDF file is still on. See the images to view what I say.
Attachment 13646

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Added after 12 minutes:

Furthermore, I test to show the QgraphicsScene in a QGraphicsView. The result is identical to the file stored in PDF format, so the bug seems to stay in the SVG storing elaboration, obtained via QSvgGenerator, a module provided with Qt.

Is it a bug?