The installation package checks if /dev/dri/renderD128 exists.
It is a passive test only. It doesn’t know if PMS can use it or not.
If you read Plex Media Server - Linux installation packaging update - Issues
You’ll see the limitations.
There is no PMS support at this time for AMD. If your drivers cause /dev/dri/renderD128 to be created, that’s why the installation reports it.
What do you think of the installation packaging so far?