Commercial release announcement: https://www.qt.io/blog/commercial-lts-qt-5.15.9-released
OpenSource release announcement: https://lists.qt-project.org/pipermail/announce/2023-April/000406.html
As usual I want to personally extend my gratitude to the Commercial users of Qt for beta testing Qt 5.15.9 for the rest of us.
The Commercial Qt 5.15.9 release introduced one bug that have later been fixed. Thanks to that, our Patchset Collection has been able to incorporate the fix for the issue  and the Free Software users will never be affected by it!
P.S: Special shout-out to Andreas Sturmlechner for identifying the fix of the issue, since I usually only pay attention to "Revert XYZ" commits and this one is not a revert but subsequent improvement