d3vnull Thank you very much.

I added this line:
Code:
XAUTHORITY=/home/krzysiek/.local/share/sddm/.Xauthority
and now it looks like:

Code:
5 7 * * *    env DISPLAY=:0 XAUTHORITY=/home/krzysiek/.local/share/sddm/.Xauthority /usr/bin/luckybackup --silent --skip-critical /home/krzysiek/.luckyBackup/profiles/default.profile > /home/krzysiek/.luckyBackup/logs/default-LastCronLog.log 2>&1
That solved my problem.