macOS VFIO
Today I finally got my macOS Catalina VM working again on Debian Sid. I basically did a complete fresh install using macOS-Simple-KVM, tweaked some settings, imported it to virt-manager then optimised.
Looking at it, what was breaking VFIO on 5.6/5.7/5.8.0 (yes I even compiled 5.8.0-rc5!) was probably the clock/pit settings, as kvm-pit using a lot of CPU was one of the symptons of the crashing, qemu did the whole install fine, then as soon as I imported into virt-manager it crashed.