Ubuntu PMS not utilizing Nvidia HW transcoding

[tom80H]

Sounds like a restriction through snap which does not provide support for the necessary drivers.

Transcoding on Nvidia 1650 Super

The snap does not include driver support for GPU’s and it isolates Plex from the one’s you installed. Be aware that the Plex install/data directory is or use to be different /var/snap/plexmediaserver/common/Library/Application Support vs /var/lib/plexmediaserver. If it is and you want to transfer your current data you will have to cp or move it to the new location, don’t forget to check file ownership afterward, should be plex.

Have you tried a plain install of Plex Media Server on your Ubuntu (using the dpkg without the abstractions)?