Darktable 3.0.1 : move to external HDD and backup thereof

On WS1, moved 2020 RAW files to /media/luc/Sea/RAW/2020. Went fine (after moving the connection to a USB2 socket -- USB1.1 was sooo slooow). Then tried to backup WS1 including the external HDD. That didn't work after changing the urbackup server group configuration, even after restart of both server and client software (no reboot). So used urbackupclientctl add-backupdir on the client, to add the directory. That seems to do the trick.