After having some trouble removing shared folders and filesystems for a crashed external backup disk, I was able to clean everything up (partly manually from config.xml).
The only issue I have left is monit complaining when booting the system:
Status failed Service mountpoint_srv_dev-disk-by-label-backup Date: Wed, 26 Jun 2019 10:23:01 Action: alert Host: odroidxu4 Description: status failed (1) -- /srv/dev-disk-by-label-backup is not a mountpoint Your faithful employee, Monit
Any idea where to clean up the remaining mountpoint apparently still listed somewhere?
There are no more references in config.xml or in fstab.