That's kind of what RISC V is. Since you can make a CPU as complex or as simple as you need it, there aren't really standard toolchains or other gadgets available.
Ive been wanting to try some more eclectic type systems with the chip shortages going on and ARM likely becoming owned fully by china im not sure how much longer the standard stuff is going to be available. I think the US still has some RISC fabs that can produce chips.
If you're just looking for an SBC, there's no real need to look past the Pi, or Odroid's offerings.
RISC V is a developer's system. We may see some mainstream boards eventually, but general purpose computing isn't really their use case.
From what i understand ARM is also a RISC instruction set with some of their own proprietary framework and instructions thrown in to address issues with using RISC instruction sets. RISC-5 looks like its a completely open source instruction set. It's probably worth it to start getting into it now and putting some weight behind it so it can be a competitor with ARM and we might see some open source processor designs go to mass production.
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