...

RV64G is supported for several popular hardware, emulated and FPGA-based platforms as a Tier 2 platform. Various feature additions and performance optimisation opportunities exist. See the upstream wiki page linked above for more details.

...

FreeRTOS

RISC-V Status

RISC-V support has been merged in FreeRTOS. A couple of boards is directly supported.

...

Linux

RISC-V Maintainers

• Palmer Dabbelt
• Albert Ou
• Paul Walmsley

...

The Linux kernel supports RV64G as well as RV32G.

...

OpenBSD

Releases

RISC-V Status

Work is in progress adding the port, with the first commit made on 23rd April 2021.