Well that’s somewhat good news. Can you provide specifics about what you tested with?
Windows build
Plex Server version
AMD driver version
Does HDR → SDR tonemapping use the GPU with hardware acceleration enabled?
Can you test what the maximum number of concurrent transcodes you can do with that APU is? Be it 4K → 4K, 4K → 1080p, 4K → 1080p with tonemapping, etc. Just curious.
Testing with a 5600G showed that at least on one occasion I had a green pixel running down the right side of the transcoded video when using hardware transcoding from 4K HDR → 1080p SDR.
HDR → SDR tonemapping still isn’t hardware accelerated, so at least with a 5600G it’s not really possible to tonemap (4K content) in real-time without buffering.