Hi,
If you install plexmediaserver on a headless box, you will need to ensure that libnvidia-glcore.so.* is installed. At the time of writing this thread required that, on an Ubuntu system, you have a package named like libnvidia-gl-* installed. The * here is in place of an nvidia driver number, which you will need to discover with something like apt find libnvidia-gl- to list all the packages that contain that term in their name or description.
For non-Ubuntu systems you will need to search your distro’s package repository for the right package that contains libnvidia-glcore.so.* shared-object library files.
Once you have libnvidia-glcore.so.* files in the right place on your system then everything should work correctly without further intervention.