Just sharing a small MiniDLNA tip I worked out, hope it saves someone some hair-pulling.
If you want to use symlinks to share files via MiniDLNA, you might find that media files appear to be served but you can't connect to them.
You need to enable a config option for this to work:
Go to the DLNA section in OMV's web GUI.
Scroll the bottom section named 'Extra options'
Type in wide_links=yes
Save and apply.