Anyway, to actually answer your question, if you need a source that the Librem doesn't have an IOMMU, then frankly you're out of your depth for this conversation.
I am saying the rest of your document you cited was riddled with errors that I could show was wrong off hand (with citations!), so any claims you make that I don't know is right, I treat with skepticism.
I'm unconvinced that you have actually looked through the source of the Librem 5, considering you didn't know it supported encryption! Hell, did you look at their product page? You can see that it has a smartcard on their product page! And yet you claimed it doesn't have "hardware backed encryption".
So either you are a) completely unaware of how to do basic research and citations or b) willfully spreading misinformation.
Just have elsewhere.
All I can do is point.