I could be wrong, but doesn't the raspberry pi require a humongous blob of unmodifiable binaries to run even linux? From what I understood, a number of hardware components are have closed source drivers and such, that made many dislike the entire platform
The Raspberry Pi requires nonfree software to start up. It can't reach the point of executing free software unless this nonfree program is part of the installed system software: https://www.fsf.org/resources/hw/single-board-computers
