I don't know if any of these have RISC-V support, but I would be interested in hearing about it. I would actually love a good distro for RV32G which is arguably a better match for FPGA softcores (and dev boards with > 4 GiB of external memory are rare)

Looks like Gentoo's is experimental [0, 1], and [2] looks relevant for NixOS.

[0]: https://wiki.gentoo.org/wiki/Project:RISC-V [1]: https://dev.gentoo.org/~dilfridge/stages/ [2]: https://nitter.net/shlevy/status/965019194759761920?lang=en