That line is only shown on Intel. Useis that normal for a AMD system? because the guide says i should see a line saying "DMAR: IOMMU enabled"
for d in /sys/kernel/iommu_groups/*/devices/*; do n=${d#*/iommu_groups/*}; n=${n%%/*}; printf 'IOMMU group %s ' "$n"; lspci -nns "${d##*/}"; done
and check if there are multiple IOMMU groups. It is not enabled if there is only one group named *
.