Some preliminary notes. This document subject to revision and renaming.
The following two guides written Mathias Huber by seem to be among the best out there:
Matthias Huber. "All you need to know about PCI passthrough in Windows 11 virtual machines on Ubuntu 22.04 based distributions". MatthiasHuber.com, 27 June 2022, https://mathiashueber.com/passthrough-windows-11-vm-ubuntu-22-04/.
Matthias Huber. "Virtual machines with PCI passthrough on Ubuntu 20.04, a straightforward guide for gaming on a virtual machine". MatthiasHuber.com, 21 June 2020, https://mathiashueber.com/pci-passthrough-ubuntu-2004-virtual-machine/.
Luxuride. "VFIO Windows install walkthrough: Looking Glass". GitLab/Luxuride, https://gitlab.com/Luxuride/VFIO-Windows-install-walkthrough/-/blob/master/LookingGlass.md.