OK, this thread needs some corrective input...
The default ownership of /dev/dri/renderD128 is root:render, with a ug=rw permission.
The Linuxserver.io Plex-container supports running as a specific user/group. Use that functionality!
Add the user you run the container as to the render group.
There is absolutely no need to change ownership or permissions on a system-device.
Also worth noting: Using an nVidia consumer GPU to transcode imposes an artificial limitation of a maximum of two concurrent transcodes. This is hardcoded into the nVidia driver. Intel QuickSync has no such limitations.
nVidia Quadro cards can do more parallel streams, use this list as a guide: https://www.elpamsoft.com/?p=Plex-Hardware-Transcoding
