If you really want Rust, check this https://github.com/r9os/r9 it is Plan 9 reimplemented in Rust (no idea about the project quality):
R9 is a reimplementation of the plan9 kernel in Rust. It is not only inspired by but in many ways derived from the original Plan 9 source code.
If "modern" means complex, I don't think it fits Plan9.
Knowing that project am I going to be rickrolled?
Which tends to be forgotten when praising Plan 9.
However the influence is quite clear, plus the Oberon-2 style methods and SYSTEM package.
Eikon•1h ago
[0] https://github.com/Barre/ZeroFS
[1] https://docs.kernel.org/filesystems/9p.html