At the other end of the scale, if anyone wants to play you can run a little openpower CPU on an FPGA with completely open source. https://github.com/antonblanchard/microwatt
It's capable of running Linux, some example docs are https://shenki.github.io/boot-linux-on-microwatt/
The toolchain consists of "apt install gcc-powerpc64le-linux-gnu" on Debian, no funny downloads. And if you want to target a Lattice ECP5 board even the FPGA tools are also all open, thanks to Yosys and friends.
All the openpower ISA spec PDFs are available for perusing on the openpower site.
It's capable of running Linux, some example docs are https://shenki.github.io/boot-linux-on-microwatt/ The toolchain consists of "apt install gcc-powerpc64le-linux-gnu" on Debian, no funny downloads. And if you want to target a Lattice ECP5 board even the FPGA tools are also all open, thanks to Yosys and friends.
All the openpower ISA spec PDFs are available for perusing on the openpower site.