After installing laptop-mode-tools, the log message appears in journal:

thinkpad:~ # journalctl -x | grep 'laptop-mode' | grep 'udev'
Apr 02 11:20:35 thinkpad laptop-mode[2198]: failed - udev not active?
Apr 02 11:20:35 thinkpad laptop-mode[2227]: failed - udev not active?
Apr 02 11:22:50 thinkpad laptop-mode[1291]: failed - udev not active?
Apr 02 11:22:50 thinkpad laptop-mode[1485]: failed - udev not active?

Some googling showed the solution, in one command:

sed -i -e 's;/sbin/udevadm;/usr/bin/udevadm;g'
/usr/share/laptop-mode-tools/modules/hdparm

It appears that laptop-mode-tools are not handling symlinks properly? Any way,
after the single command the message disappered.