OpenFirmware came out of OpenSPARC and is also used by POWER too. Parts of it are used in ARM and RISC-V today (mostly DeviceTree, though arguably quite badly).
Nobody actually wants to make good cores for cheap. Nobody wants to make compatible systems unless forced to. That's why ARM and RISC-V are fragmented messes.
I would personally love to see more Power Systems based projects. Everything is out there, just someone has to want to do something with it.
Fedora Linux even fully supports POWER8+ little-endian systems, and Fedora KDE offers a live ISO you can install on something like a Talos Workstation.
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