A Proxmox hookscript (/var/lib/vz/snippets/second-gpu.sh) that releases my NVIDIA GPU after the VM stops so that I can display the host terminal.

second-gpu.sh

#!/bin/bash
SECOND_GPU="0000:01:00.0"

# First argument is the vmid
# Second argument is the phase
VMID="$1"
shift
PHASE="$1"

if [ "$PHASE" = "post-stop" ]; then
        sleep 2

        while [ -d "/sys/bus/pci/drivers/vfio-pci/$SECOND_GPU" ]; do
                echo "$SECOND_GPU" > /sys/bus/pci/drivers/vfio-pci/unbind 2>&1
        done

        while [ ! -d "/sys/bus/pci/drivers/nouveau/$SECOND_GPU" ]; do
                echo "$SECOND_GPU" > /sys/bus/pci/drivers/nouveau/bind 2>&1
        done
fi