https://en.wikipedia.org/wiki/Loongson
They have quite a bit more support in FOSS than Cavium's Octeon processor boards. Which are also cool:
http://www.cavium.com/OCTEON-III_CN7XXX.html
CHERI project modifies open-source BERI core on Terasic device:
https://www.cl.cam.ac.uk/research/security/ctsrd/cheri/
Note: Barely gets more open and extensible than that outside RISC-V, etc. Those don't run FreeBSD, IIRC.
So, MIPS is far from dead even if MIPS32's limitations sucked. :)