First of all, what is that actually? PCI passthrough describes the process of passing PCI (e) components directly to a virtual machine. This makes it part of the VM and also directly recognizes it as hardware. In the standard, the function is not configured in the Debian substructure of Proxmox. Proxmox also reports this when we want to give a VM a PCI device.

So we follow up on the request and pull the entry from the wiki. PCI-Passthrough advise.
To the terminal and the configuration files. First will FOOD personalized.

nano /etc/default/grub

Online
GRUB_CMDLINE_LINUX_DEFAULT="quiet"

let’s add a parameter after “quiet” to activate IOMMU additional.
The result should look like this:
GRUB_CMDLINE_LINUX_DEFAULT="quiet intel_iommu=on"

Then the bootloader configuration is updated.
update-grub

We go to the next file.
nano /etc/modules

The following is inserted below the entire comment line (the lines with #):
vfio
vfio_iommu_type1
vfio_pci
vfio_virqfd

Support for “IOMMU remapping” must be available for PCI devices to pass through. This is checked here with.
dmesg | grep 'remapping'

Feedback comes
"DMAR-IR: Enabled IRQ remapping in x2apic mode" ('x2apic' can be different on old CPUs, but should still work)

the function is supported.

Next, a file is created. This is used to lock the graphics drivers on the host so that it cannot load them and thus damage the graphics cards. This can potentially eliminate issues with GPU-to-VM pass-through.

In the File.
nano /etc/modprobe.d/blacklist.conf

we enter the following.
blacklist radeon
blacklist amdgpu
blacklist nouveau
blacklist nvidia
blacklist nvidiafb

Last wish initramfs updated.
update-initramfs -u -k all

In the end, the host will reboot.
reboot