Huh, I have the exact same CPU and RAM config as you, I should try booting Ubuntu myself as well as a couple other distros to see if I can replicate the same issue OP is having. I’ll right back with my findings.
Can you share where you put the iommu=pt thing? The whole grub boot parameters
I have Ryzen 5 3500c with 4gb and 128gb NVMe. So, maybe the same CPU but different ram and storage.