Don't know if these would match the 'similarly simple' requirement but there are certainly RISC-V cores written in either Clash: https://github.com/adamwalker/c

Don't know if these would match the 'similarly simple' requirement but there are certainly RISC-V cores written in either Clash: https://github.com/adamwalker/clash-riscv https://github.com/adamwalker/clash-riscv https://github.com/losfair/Violet https://github.com/losfair/Violet or Bluespec: https://bluespec.com/category/risc-v/ https://bluespec.com/category/risc-v/