GPU passthrough not working

[fszadmin]

My issue is that although Transcoding with NVIDIA-NVENC is activated jellyfin is not using my GPU for transcoding.

I tried to keep the config as simple as possible to first of all get it running. But I need jellyfin to run on an lxc, it cant run on the host.

I am running Jellyfin 10.10.7 on an LXC of Proxmox with Debian 12 (bookworm) OS. The GPU is NVIDIA Quadro RTX 5000.
This is the config of my LXC:

arch: amd64
cores: 4
features: nesting=1
hostname: Jellyfin
memory: 8000
mp0: Movies:114/vm-114-disk-0.raw,mp=/mnt/movies,backup=1,size=1000G
net0: name=eth0,bridge=vmbr0,firewall=1,hwaddr=BC:24:11:7A2:B9,ip=dhcp,type=veth
onboot: 1
ostype: debian
rootfs: Container:114/vm-114-disk-0.raw,size=60G
swap: 8000
unprivileged: 0
lxc.cgroup2.devices.allow: c 195:0 rwm
lxc.cgroup2.devices.allow: c 195:255 rwm
lxc.cgroup2.devices.allow: c 509:0 rwm
lxc.cgroup2.devices.allow: c 509:1 rwm
lxc.cgroup2.devices.allow: c 234:1 rwm
lxc.cgroup2.devices.allow: c 234:2 rwm
lxc.mount.entry: /dev/nvidia0 dev/nvidia0 none bind,optional,create=file
lxc.mount.entry: /dev/nvidiactl dev/nvidiactl none bind,optional,create=file
lxc.mount.entry: /dev/nvidia-uvm dev/nvidia-uvm none bind,optional,create=file
lxc.mount.entry: /dev/nvidia-uvm-tools dev/nvidia-uvm-tools none bind,optional,create=file
lxc.mount.entry: /dev/nvidia-caps/nvidia-cap1 dev/nvidia-caps/nvidia-cap1 none bind,optional,create=file
lxc.mount.entry: /dev/nvidia-caps/nvidia-cap2 dev/nvidia-caps/nvidia-cap2 none bind,optional,create=file
lxc.mount.entry: /usr/bin/nvidia-smi usr/bin/nvidia-smi none bind,optional,create=file
lxc.mount.entry: /usr/lib/x86_64-linux-gnu/libnvidia-ml.so.580.95.05 usr/lib/x86_64-linux-gnu/libnvidia-ml.so.580.95.05 none bind,ro,create=file

The hardware and the driver are visible inside the lxc. I have installed jellyfin directly in the lxc. There is no docker involved.
My ffmpeg version ist: 

ffmpeg version 7.1.2-Jellyfin Copyright © 2000-2025 the FFmpeg developers
built with gcc 12 (Debian 12.2.0-14+deb12u1)

This is the log when I enable transcoding and start watching a movie:

[2025-10-16 07:33:27.326 +00:00] [INF] User policy for "jellyfin". EnablePlaybackRemuxing: True EnableVideoPlaybackTranscoding: True EnableAudioPlaybackTransco>
[2025-10-16 07:33:27.921 +00:00] [ERR] Extracting keyframes from "/mnt/movies/Resident Evil (2002).mkv" using matroska metadata failed
System.IO.EndOfStreamException: Attempted to read past the end of the stream.
  at NEbml.Core.VInt.Read(Stream source, Int32 maxLength, Byte[] buffer)
  at NEbml.Core.EbmlReader.ReadVarInt(Int32 maxLength)
  at NEbml.Core.EbmlReader.ReadElement()
  at NEbml.Core.EbmlReader.ReadAt(Int64 position)
  at Jellyfin.MediaEncoding.Keyframes.Matroska.MatroskaKeyframeExtractor.GetKeyframeData(String filePath)
  at Jellyfin.MediaEncoding.Hls.Extractors.MatroskaKeyframeExtractor.TryExtractKeyframes(String filePath, KeyframeData& keyframeData)
[2025-10-16 07:33:28.095 +00:00] [INF] Current HLS implementation doesn't support non-keyframe breaks but one is requested, ignoring that request
[2025-10-16 07:33:28.113 +00:00] [INF] "/usr/lib/jellyfin-ffmpeg/ffmpeg" "-analyzeduration 200M -probesize 1G -fflags +genpts -f matroska  -i file:\"/mnt/movie>
[2025-10-16 07:33:42.391 +00:00] [INF] Stopping ffmpeg process with q command for "/var/cache/jellyfin/transcodes/57d9e37e4b742f0dae5ad38fbcea4b60.m3u8"
[2025-10-16 07:33:42.959 +00:00] [INF] FFmpeg exited with code 0
[2025-10-16 07:33:42.961 +00:00] [INF] Deleting partial stream file(s) "/var/cache/jellyfin/transcodes/57d9e37e4b742f0dae5ad38fbcea4b60.m3u8"
[2025-10-16 07:33:44.991 +00:00] [INF] Playback stopped reported by app "Jellyfin Web" "10.10.7" playing "Resident Evil". Stopped at "12288" ms

Please help me getting my GPU to work.