Hi,

You might try uninstalling mesa-va-drivers and replacing with this:
mesa-va-drivers-freeworld

one of my 2 machines was ok and a 2nd one looked closer to what yours
looked like.

And replacing with freeworld it now looks much better and has a lot
more accelerators.

I've done that, and now it definitely appears to have more support, but alas, it made no difference.

$ vainfo The.Equalizer.mkv
Trying display: wayland
Trying display: x11
libva info: VA-API version 1.18.0
libva info: Trying to open /usr/lib64/dri/radeonsi_drv_video.so
libva info: Found init function __vaDriverInit_1_18
libva info: va_openDriver() returns 0
vainfo: VA-API version: 1.18 (libva 2.18.2)
vainfo: Driver version: Mesa Gallium driver 23.1.8 for AMD Radeon RX 570 Series (polaris10, LLVM 16.0.6, DRM 3.54, 6.5.5-200.fc38.x86_64)
vainfo: Supported profile and entrypoints
      VAProfileMPEG2Simple            : VAEntrypointVLD
      VAProfileMPEG2Main              : VAEntrypointVLD
      VAProfileVC1Simple              : VAEntrypointVLD
      VAProfileVC1Main                : VAEntrypointVLD
      VAProfileVC1Advanced            : VAEntrypointVLD
      VAProfileH264ConstrainedBaseline: VAEntrypointVLD
      VAProfileH264ConstrainedBaseline: VAEntrypointEncSlice
      VAProfileH264Main               : VAEntrypointVLD
      VAProfileH264Main               : VAEntrypointEncSlice
      VAProfileH264High               : VAEntrypointVLD
      VAProfileH264High               : VAEntrypointEncSlice
      VAProfileHEVCMain               : VAEntrypointVLD
      VAProfileHEVCMain               : VAEntrypointEncSlice
      VAProfileHEVCMain10             : VAEntrypointVLD
      VAProfileJPEGBaseline           : VAEntrypointVLD
      VAProfileNone                   : VAEntrypointVideoProc

I also just tried to play two regular 1080p videos at the same time using vlc, and it also showed the same problem where the system becomes effectively unusable.

Thanks,
Alex