`actions/setup-python` fails on riscv64 runners because `actions/python-versions` does not provide pre-built Python binaries for `linux/riscv64`: ``` Error: The version '3.11 - 3.14' with architecture 'riscv64' was not found for Ubuntu 24.04. ``` This blocks all Python CI workflows on riscv64 GitHub Actions runners. RISC-V self-hosted runners are becoming available through the [RISE RISC-V runners](https://github.com/apps/rise-risc-v-runners) program, used by projects like numpy, llama.cpp, and pytorch. CPython supports riscv64 as a Tier 3 platform and builds natively on current hardware. Ideally, `actions/python-versions` would add riscv64 to its build matrix. As a shorter-term fix, `setup-python` could fall back to system Python when pre-built binaries are unavailable for the current architecture.