The oldest kernel I found at the linked repo is 6.8.4-rc1 and it shows the problem. Where can I get older kernels? As far as I remember before migrating to KDE6 I was not using hybrid sleep, but with KDE6 problems with returning from sleep appeared therefore I needed to switch on hybrid sleep to save my work. The KDE bug report: https://bugs.kde.org/show_bug.cgi?id=484808 (see my last comment). Maybe it is not just a KDE bug?