Just to be pedantic, nix actually supports macOS and runs on top of Apple's kernel and userland (which I've tried, which is why I'm being pedantic), it's nixOS which runs at ring 1 that's being discussed here.
The biggest issue is that M1 is undocumented Apple Silicon. It has to be fully reverse engineered, primarily by the Asahi Linux team.
Other Linux distros will have to piggyback off the work of Asahi, and I think that generally they're avoiding jumping in yet because the hardware support is not very mature.
As much as I love the project, the work is far from done. Any macOS update can change the firmware of the GPU or the display controller, which would break the Asahi driver. And there are going to be a lot of macOS updates for at least the next five years.
I'm cautiously hopeful. Apple did break things a couple times already, but along with one of the breakages, they also introduced a new "we won't break this thing again" mode.