10 years of shipped code for multiple platforms (x86, ARMv7, ARMv8) is not varporware. Based on software experience with existing platforms, they have created an open hardware RISC-V core which requires custom software to achieve energy effiency with improved performance, https://spectrum.ieee.org/snitch-riscv-processor-6x-faster

> Snitch proved to be 3.5 times more energy efficient and up to six times faster than the others.. "While we could already demonstrate a very energy-efficient and versatile 8-core Snitch cluster configuration in silicon, there are exciting opportunities ahead in building computing platforms scalable to thousands of Snitch cores, even spreading over multiple chiplets," says Zaruba, noting that his team is currently working towards this goal.

https://github.com/pulp-platform/snitch

It is on most mainstream computers, even though it is the way in most high integrity computing deployments.