Earlier quoted context omitted.
It is you who is confused here. The first link is completely irrelevant to the Librem 5, and the second one points to a thread where the actual information present has been written by me. The only non-free piece of code executed by the ARM Cortex-A53 cluster on the Librem 5 is the SoC's mask ROM bootloader. Once the control is passed to u-boot/ATF there is not a single non-free blob that runs there. Some peripherals…
Ah. I see. So the blobs are loaded into the separate microprocessors. Either way, it's the same as pretty much any modern phone, where the modem (and other secondary processors) are running some proprietary firmware and is communicating with the OS processor. I don't see how it's different from running a free open-source ASOP OS. On the mainstream Android devices, the wireless hardware is also isolated and communicat…
> at that point you still are trusting external communication to those devices with their proprietary blobs
Just as you do with any kind of peripheral, whether it implements what it's doing purely in hardware or with an embedded microcontroller.
> There's some debate as to whether the USB stack for communication to the modem is less secure than IOMMU as well.
You can have "some debate" on absolutely anything, but that doesn't yet mean it makes any sense. You have communication protocols on top of IOMMUs as well which are subject to exactly the same security considerations as potential exploits in the USB stack, so whatever debate you're referring to is unlikely to be held in good faith. I wonder why you mention it unprompted, as it's fairly off-topic here.