[ponkotsu]

library updated just fine on the MiniPC (with MySQL installed on this device, external hard drive plugged into this).

(...)

i get 'this file is no longer available' when i try to play.

Don't give up yet. We're almost there -- at least the MySQL connection is working from both devices.

2 questions:

Does the MiniPC have a static IP address or does it get its IP address via DHCP? If via DHCP, you will probably want to set a reservation for the MiniPC in your DHCP server (usually your router) so that it always has the 192.168.1.98 address. This way, the Pi will always be looking in the right place for the MySQL database.

Secondly, when you scanned your movies & tv shows in to the database, were they scanned directly from the external hard drive (eg: D:\Media\Movies\Avatar (2009)\Avatar (2009).mkv) or from the external hard drive via a shared folder source (eg: smb://DESKTOP-4B2ODFK/Movies/Avatar (2009)/Avatar (2009).mkv or smb://192.168.1.98/Movies/Avatar (2009)/Avatar (2009).mkv)? If directly (aka via a drive letter), then the Pi won't be able to access the file because there's no D: drive (for example) on the Pi. On your MiniPC, you'd have to share (as an example, I don't know your actual folder structure) the folder containing your media. In a Windows world, this would mean you'd be able to access it with something like \\DESKTOP-4B2ODFK\Media or \\192.168.1.98\Media. In Kodi, you'd set the movies' video source as, for example, smb://192.168.1.98/Media/Movies. This source would then be able to be understood and accessible by both the MiniPC and the Pi (and any other Kodi devices you later choose to add at home).

Sorry if you already did all of this or if it was too dumbed-down. It was just the first thing that came to mind.