See this thread: Any chance for updated AMD (Mesa Gallium) drivers?
The transcoder update must happen first. Then Intel driver updates are next on the schedule.
The transcoder update available as a forum preview: Transcoder Upgrade Forum Preview. There is no announced timeline when it will be in a beta release or when Intel drivers will be updated.
On Linux, Plex supports AMD GPUs for transcoding SDR video. See Plex Media Server - #589 by Ridley. I do not know if all their GPUs are supported.
Edit: Additional information on how Plex currently supports AMD on Linux: AMD GPU Hardware acceleration - #6 by ChuckPa.
iGPU vs dGPU doesn’t matter. Plex uses the same drivers to address either.
