Jellyfin, CUDA & NixOS : Unable to transcode

I am posting here in the hopes that someone can see my silly mistake and go on my way (feeling silly but with one less problem). Any help is welcomed ! Description of the bug I am faced with exactly the same bug as jellyfin: NVENC transcoding does not work · Issue #152008 · NixOS/nixpkgs · GitHub Of course just as in jellyfin: NVENC ffmpeg fails when called by jellyfin but works as user · Issue #141298 · NixOS/nixpkgs · GitHub, if I sudo -u jellyfin <ffmpeg command bellow> everything runs so… ...