Using the new support for Windows 11's dark mode via the Fusion style and not using any custom styling, all links are dark blue on gray and therefore almost illegible. This affects both instances of QLabel as well as text rendered via QTextBrowser.

Should be easy enough to reproduce: build an app based on 6.5.0 for Windows, run QApplication::setStyle(Q("Fusion")); & add some QLabel-based links. Set Windows' app color mode to "dark".