This is an unsupported variant, as x86 is the only CPU architecture being targeted for R1. It is provided for development and testing purposes only. Releasing software that requires these unsupported builds is discouraged.
The RISCV64 port is in an early state and depends on a functioning RISCV64 EFI BIOS. When booting this image written to a USB flash drive on devices like the SiFive Unmatched, a u-boot firmware SD card is required to provide an EFI bios.
For more information on missing packages, image and archive formats, etc., please refer to this site's main page.
Unsupported RISCV64 Builds