I have Proxmox running on top of a clean Debian install on my NUC, I wanted to allow Plex to use the hardware decoding and it got a bit funny trying to do that with Plex running in a VM, so it runs on the host and I use VMs for other stuff

It's very easy to do this with LXC containers in Proxmox now, as passing devices to a container is now possible from the UI.

Just as easy with VMs, just have to pass the device to the VM

I have an Intel (12th Gen i5-12450H) mini-pc and at first had issues getting the GPU firmware loaded and working in Debian 12. However upgrading to Debian 13 (trixie) and doing apt update and upgrade resolved the issue and was able to pass the onboard Intel GPU through Docker to a Jellyfin container just fine. I believe the issue is related to older linux kernels and GPU firmware compatibility. Perhaps that’s your issue.