Yes, this seems to be an issue with newer versions of Plex (> 1.22.0)
I was very excited when Plex released support for hardware transcoding of HDR content. I made sure to install the necessary OpenCL bits on my Plex server (running Fedora 34) and confirmed that transcoding HEVC HDR content to H264 SDR was assisted by hardware - as evidenced by Tautulli and significantly reduced CPU usage on my server.
If I downgrade to plexmediaserver-1.22.0.4163-d8c4875dd (found here: https://github.com/axlecrusher/plex_download_urls), transcoding is done in hardware. Example:
STREAM
Transcode (Speed: 3.4)
CONTAINER
Converting (MKV MP4)
VIDEO
Transcode (HEVC (HW) 1080p HDR H264 (HW) 1080p SDR)
AUDIO
Transcode (AAC 7.1 AAC Stereo)
SUBTITLE
None
I tried a number of newer Plex builds, and everything after 1.22.0.4163-d8c4875dd, starting with 1.22.1.4228-724c56e62 goes back to software transcoding. The latest build, plexmediaserver-1.24.2.4973-2b1b51db9, is included. Example:
STREAM
Transcode (Speed: 0.7)
CONTAINER
Converting (MKV MP4)
VIDEO
Transcode (HEVC 1080p HDR H264 1080p SDR)
AUDIO
Transcode (AAC 7.1 AAC Stereo)
SUBTITLE
None
Some info from my server in case it helps:
uname -a
Linux x.x.x.x 5.13.13-200.fc34.x86_64 #1 SMP Thu Aug 26 17:06:39 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux
rpm -qa | grep opencl
opencl-headers-3.0-7.20210216gitd1b936b.fc34.noarch
intel-igc-opencl-1.0.8517-1.fc34.x86_64
intel-opencl-21.35.20826-1.fc34.x86_64
clinfo -l
Platform #0: Intel(R) OpenCL HD Graphics
`-- Device #0: Intel(R) UHD Graphics 630 [0x3e91]
cat /proc/cpuinfo
processor : 0
vendor_id : GenuineIntel
cpu family : 6
model : 158
model name : Intel(R) Core(TM) i3-8100 CPU @ 3.60GHz
stepping : 11
microcode : 0xea
cpu MHz : 2288.021
cache size : 6144 KB
physical id : 0
siblings : 4
core id : 0
cpu cores : 4
apicid : 0
initial apicid : 0
fpu : yes
fpu_exception : yes
cpuid level : 22
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx pdpe1gb rdtscp lm constant_tsc art arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc cpuid aperfmperf pni pclmulqdq dtes64 monitor ds_cpl vmx est tm2 ssse3 sdbg fma cx16 xtpr pdcm pcid sse4_1 sse4_2 x2apic movbe popcnt tsc_deadline_timer aes xsave avx f16c rdrand lahf_lm abm 3dnowprefetch cpuid_fault epb invpcid_single pti ssbd ibrs ibpb stibp tpr_shadow vnmi flexpriority ept vpid ept_ad fsgsbase tsc_adjust bmi1 avx2 smep bmi2 erms invpcid mpx rdseed adx smap clflushopt intel_pt xsaveopt xsavec xgetbv1 xsaves dtherm arat pln pts hwp hwp_notify hwp_act_window hwp_epp md_clear flush_l1d
vmx flags : vnmi preemption_timer invvpid ept_x_only ept_ad ept_1gb flexpriority tsc_offset vtpr mtf vapic ept vpid unrestricted_guest ple pml ept_mode_based_exec
bugs : cpu_meltdown spectre_v1 spectre_v2 spec_store_bypass l1tf mds swapgs itlb_multihit srbds
bogomips : 7200.00
clflush size : 64
cache_alignment : 64
address sizes : 39 bits physical, 48 bits virtual
power management:
...
