I have Kröhnkite KWin script (https://github.com/anametologin/krohnkite) installed and activated.
As seen at https://github.com/anametologin/krohnkite/blob/0.9.8.2/res/main.qml#L52 it outputs log message using console.log():
console.log("KROHNKITE: starting the script");

However after setting "KWin Scripting" log level to "Full Debug" and removing "*.debug=false" rule from Custom Rules in KDebugSettings I don't see this (and other log messages from this script) message in KSystemLog.

Originally I raised this problem at https://github.com/anametologin/krohnkite/issues/94
Related:
https://www.reddit.com/r/kde/comments/15jm7me/debug_printing_in_kwin_scripts/
https://www.reddit.com/r/Fedora/comments/15kiv2c/kde_or_fedora_issue_print_in_kwin_script_not/
https://discuss.kde.org/t/wayland-and-plasmashell-are-spamming-my-syslog/21391


[piotr@demon]~% kinfo
Operating System: Fedora Linux 41
KDE Plasma Version: 6.2.0
KDE Frameworks Version: 6.7.0
Qt Version: 6.7.2
Kernel Version: 6.11.3-300.fc41.x86_64 (64-bit)
Graphics Platform: Wayland
Processors: 12 × AMD Ryzen 5 7600 6-Core Processor
Memory: 14.8 GiB of RAM
Graphics Processor: AMD Radeon Graphics