I had a roadblock today and figured it out, but I want to understand the difference. I configured now three systems with iommu and pci-passthrough. Everytime appending intel_iommu=on at /etc/kernel/cmdline was enough. Those were on a:
ASUS Prime Z590-P
MSI MEG Z590 ACE
ASUS B450M-K II
MSI MEG...
