[AGLyons]

So I have A Rasp4 acting as a client pulling the UPNP library from a Libreelecx64 box. All the media is on a Synology NAS. 

The Rasp used to have all the same sources defined as direct SMB as the LE box but I removed them all and cleaned the DB. What I've noticed is the Rasp4 using UPNP does not show movies anymore and there is no way to define the UPNP source as movies. I have widgets on my movies page and those are now empty. Clicking the movies menu item now brings me to the video sources page. 

While I appreciate the ability to use UPNP as a source, why does it work differently than a regular source? Is there a way to change this behaviour?

This all started as I wanted to have a synced library between the two boxes and I tried to set up an external DB but that was a nightmare to get working. If UPNP is working as it was designed is there a simpler approach to getting an external DB working?

PS. My attempts to get a MariaDB working looked to me as if the advancedsettings.xml file was being ignored. When I checked, Kodi never created any tables in the DB when I started it back up. I wish there was some kind of notification, maybe on the info page, that it was using an external DB.

[Klojum]

as if the advancedsettings.xml file was being ignored.

The advancedsettings.xml file is only ignored when there are errors in it. You can confirm that by checking Kodi's log file.

UPnP is not a 'primary' source in Kodi. It feeds off the video database that is filled using SMB, NFS, FTP, or whatever file protocol.

Setting up a MariaDB database is almost foolproof when installing the MariaDB add-on onto a device running LibreELEC. For example, a Raspberry Pi or some other (old) PC. More info on that can be found on the LibreELEC forum.