1) In your PC/Laptop/Server BIOS make sure the following is enabled in the BIOS:

Intel VT-d & VT-x – Intel Compatible list
All AMD CPUs from Bulldozer onwards should be compatible.

2) Get device IDs:
lspci -nn

3) Enable IOMMU in GRUB (check Intel or AMD commands below - choose the right one)
nano /etc/default/grub
GRUB_CMDLINE_LINUX_DEFAULT="quiet intel_iommu=on iommu=pt"
GRUB_CMDLINE_LINUX_DEFAULT="quiet amd_iommu=on"
save and exit

5) run the command "update-grub"
now reboot

6) Enable VFIO Modules
nano /etc/modules
Add the following modules:
vfio
vfio_iommu_type1
vfio_pci
vfio_virqfd
Then, save and exit

Next run:
update-initramfs -u -k all
and reboot

7) GPU Isolation From the Host (amend the below to include the IDs of the device you want to isolate)
echo "options vfio-pci ids=10de:1381,10de:0fbc disable_vga=1" > /etc/modprobe.d/vfio.conf

8) Blacklist GPU drivers (here are all that you would ever need)
echo "blacklist radeon" >> /etc/modprobe.d/blacklist.conf 
echo "blacklist nouveau" >> /etc/modprobe.d/blacklist.conf 
echo "blacklist nvidia" >> /etc/modprobe.d/blacklist.conf 
echo "blacklist nvidiafb" >> /etc/modprobe.d/blacklist.conf
echo "blacklist nvidia_drm" >> /etc/modprobe.d/blacklist.conf

9) Create a new VM and add the GPU via hardware menu
You may need to set it as primary GPU
You may need to add a ROM BAR