Step by Step tasks:

Step 1: Edit GRUB
  Execute: nano /etc/default/grub
     Change this line from
   GRUB_CMDLINE_LINUX_DEFAULT="quiet"
     to
   GRUB_CMDLINE_LINUX_DEFAULT="quiet intel_iommu=on iommu=pt pcie_acs_override=downstream,multifunction nofb nomodeset video=vesafb:off,efifb:off"
  Save file and exit the text editor

Step 2: Update GRUB
  Execute the command: update-grub

Step 3: Edit the module files
  Execute: nano /etc/modules
     Add these lines:
   vfio
   vfio_iommu_type1
   vfio_pci
   vfio_virqfd
  Save file and exit the text editor

Step 4: IOMMU remapping
 a) Execute: nano /etc/modprobe.d/iommu_unsafe_interrupts.conf
     Add this line:
   options vfio_iommu_type1 allow_unsafe_interrupts=1
     Save file and exit the text editor
 b) Execute: nano /etc/modprobe.d/kvm.conf
     Add this line:
   options kvm ignore_msrs=1
  Save file and exit the text editor

Step 5: Blacklist the GPU drivers
  Execute: nano /etc/modprobe.d/blacklist.conf
     Add these lines:
   blacklist radeon
   blacklist nouveau
   blacklist nvidia
   blacklist nvidiafb
  Save file and exit the text editor

Step 6: Adding GPU to VFIO
 a) Execute: lspci -v
     Look for your GPU and take note of the first set of numbers
 b) Execute: lspci -n -s (PCI card address)
   This command gives you the GPU vendors number.
 c) Execute: nano /etc/modprobe.d/vfio.conf
     Add this line with your GPU number and Audio number:
   options vfio-pci ids=(GPU number,Audio number) disable_vga=1
  Save file and exit the text editor

Step 7: Command to update everything and Restart
 a) Execute: update-initramfs -u
 b) Then restart the your Proxmox Node