...
RISC-V support has been merged in FreeRTOS. A couple of boards is directly supported.
...
Haiku
Haiku has been ported to RISC-V: https://www.haiku-os.org/blog/kallisti5/2021-11-07_booting_our_risc-v_images/
Illumos
Illumos has been ported to the Allwinner D1: https://github.com/n-hys/illumos-gate/wiki/Allwinner-D1-Nezha
Linux
RISC-V Maintainers
- Palmer Dabbelt
- Albert Ou
- Paul Walmsley
...
The Linux kernel supports RV64G as well as RV32G.
...
Oberon
There is an Oberon port for RISC-V, e.g., for the Bouffalo Lab BL808: http://oberon.wikidot.com/project-oberon-v
OpenBSD
Releases
RISC-V Status
...
- https://www.openbsd.org/riscv64.html
- https://www.openbsd.org/papers/Porting_OpenBSD_to_RISCV_FinalReport.pdf
xv6
...
Plan 9
Plan 9 ports exist; see also: https://ntnuopen.ntnu.no/ntnu-xmlui/bitstream/handle/11250/2902876/no.ntnu:inspera:74730513:31541262.pdf?sequence=1
Haiku
Haiku has been ported to RISC-V: https://www.haiku-os.org/blog/kallisti5/2021-11-07_booting_our_risc-v_images/
Oberon
There is an Oberon port for RISC-V, e.g., for the Bouffalo Lab BL808: http://oberon.wikidot.com/project-oberon-v
Illumos
...
xv6
There are multiple RISC-V ports of xv6, including one for the Allwinner D1: https://github.com/n-hysmichaelengel/illumos-gate/wiki/Allwinner-D1-Nezhaxv6-d1