/lib/udev/rules.d/61-kde-bluetooth-rfkill.rules is in libkf5bluezqt-data 5.44.0-0ubuntu1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 | # Get access to /dev/rfkill for users
# See https://bugzilla.redhat.com/show_bug.cgi?id=514798
#
# Simplified by Kay Sievers
# https://bugzilla.redhat.com/show_bug.cgi?id=733326
KERNEL=="rfkill", SUBSYSTEM=="misc", TAG+="uaccess"
|