Hm. The backup seems to work great. However, I get a lot of file access errors when I try to backup my home directory on manjaro linux. What are the adviced file permissions to have duplicati run without these errors?
UPDATE feb 7. The problem is solved. It turned out that the duplicati.service file installed by the AUR package contained a user=dupicati and group=duplicati statement. I removed both lines and now the service runs as root (as is normal for systemd started services).