Lots of blabla, and I still don't see any of my requested listings.
'Friendly' neighbor, eh? Forgive me Klojum as I wanted to try and solve the issue without going into measures such as you suggested (I'm unfamiliar with using SSH and commands). Anyway, I did manage to finally solve the issue. I noticed a setting in the NUC bios called UEFI Shell which was turned off (as it's the default setting). I turned it on, booted to USB LibreELEC and saw the C Drive with my files. For what it's worth, other BIOS settings which can be relevant were (Legacy Mode: off, Secure Boot: off, enable USB along with UEFI Shell via Boot Configuration).
I should really look into SSH and those commands but haven't had the time to learn but the basics of OpenELEC/LibreELEC/Kodi.
UPDATE: The problem came back. I decided to go with the latest Alpha build (having used the old Beta release from the get-go) and now everything's working. It's funny how the Beta release is promoted as a stable release which most people should use while Alpha builds are promoted as unstable. However, many seem to go with Alpha builds and now, after trying the latest build, I will not be going back to 'stable' Beta builds.