Shame RISC-V is not ready yet
If the GNOME foundation wanted a system that was completely free from proprietary software (and firmware) then (ideally) it should be running on a RISC-V processor (MIPS-like open instruction set architecture licensed under BSD license) - but obviously that is not an option - yet. gcc 7.1 will have full RISC-V support and RISC-V support is planned for the 4.15 release of the Linux. Obviously way in the future but it could be something that a freedom oriented smart phone should encourage.