I'm really lost here. There seems to be no possible way of bootstrapping any kind of armv7l nix environment.
 - Qemu building doesn't work, because it gets stuck
 - the armv7l tarball from the PR doesn't work
 - nothing mentioned in the wiki works
 - nothing mentioned on discourse works.

It seem the only way to get an armv7l nix is building it with an existing armv7l nix which is impossible to obtain without an armv7l nix. Chicken Egg Problem