If you are having issues with GPU transcoding in emby and your GPU permission keep changing after reboot use the following commands to fix the permission.
Run the following command inside your proxmox shell.
nano /etc/udev/rules.d/99-renderD128-permissions.rules
Add the following to the file
KERNEL=="renderD128", MODE="0777"
CTRL + O then Enter to save the changes to the file.
Now run the following command
udevadm control --reload-rules
Run the following command
udevadm trigger