I recently had to get GPU transcoding in Plex to work. The setup involved running Plex inside a Docker container, inside of an LXC container, running on top of Proxmox. I found some general guidelines online, but none that covered all aspects (especially dual layer of virtualization). I ran into a few challenges to get this working properly, so I’ll attempt to give a complete guide here.
I’ll assume you’ve got Proxmox and LXC set up, ready to go, running Debian 11 (Bullseye). In my example I’ll be running LXC container named docker1 (ID 101) on my Proxmox host. Everything will be headless (i.e. no X involved). The LXC will be privileged with fuse=1,nesting=1 set as features. I’ll use a Nvidia RTX A2000 as the GPU. All commands will be run as root.