I noticed the same and believe this is related: [SOLVED] Plex doesnt do HW transcoding on Ubuntu 18.04 with i9-9900 (tone mapping related) - #21 by MrSliff.
I guess what it means is that you won’t be able to have hardware transcoding as long as you don’t install these dependencies.
More info on hardware transcoding can be found here: Using Hardware-Accelerated Streaming | Plex Support
