[posguy]

The PinePhone has the same security properties as the Nokia N900 where the modem is connected over USB rather than an interface with direct memory access (eg: PCIe) where the proprietary software running on the modem can read anything in main memory.

[fragileone]

IOMMU groups are supposed to compartmentalise modems here, but as far as I know this tends to be blackboxed on Qualcomm processors.