according to https://wiki.debian.org/RaspberryPi :
"A binary blob used by the GPU must be present on the SD card for the system
to boot."
"Debian armhf will work (with a custom kernel)."
My understanding of this is the fully free armhf version does not work out of
the box. You have to include proprietary software to be able to boot the Pi.
Please correct me if I'm wrong.
Raspbian provided by the Raspberry Pi Foundation is basically Debain + 2MB
huge binary bloob necessary to start + additional non-free software including
Oracle Java and Wolfram Mathematica.
The Raspberry Pi is invitingly cheap but in terms of freedom it sadly comes
off badly.
Here https://www.fsf.org/resources/hw/single-board-computers you can find a
rating of some single-board computers concerning freedom.
I'd recommend you the Beaglebone Black. As far as I know you can run this
device with only free software. The only downside of this board is the "low"
computing power compared to a new Rasperry Pi.
