Installing x64 OS with x86 UEFI


I am trying to install nixos 21.05, on a old iMac with an Intel Core 2 CPU. Using the 32bits minimal iso image, the computer is booting.

However, I can’t manage to install x64 os which seems to be required for some applications.

There is a thread here explaining one way to do it. However when I tried to install I get the following error:

error: a 'x86_64-linux' with features {} is required to build '/nix/store/wfy2mraidsd7k7pqj9pmrafyxa0y8mhh-alsoft.conf.drv', but I am a 'i686-linux' with features {benchmark, big-parallel, kvm, nixos-test}

I am using the following configuration.nix

One other thing that I don’t quite understand.
Launching the install needs to be done using:

$ sudo NIXPKGS_ALLOW_UNFREE=1 nixos-install

For some reason nixos-install doesn’t catch

nixpkgs.config.allowUnfree = true;