I think it's more nuanced. SMP and hyperthreading are risky for security. Closed firmware is also concerning. Older systems without these architectural feature

I think it's more nuanced. SMP and hyperthreading are risky for security. Closed firmware is also concerning. Older systems without these architectural features are more difficult to abuse. I would find one of these if I needed a secure SSH CA for myself, and use OpenBSD. I probably couldn't get away with that in a larger organization.